When talking about Allstate's Mayhem campaign, Nina Abnee gets right to the point. "We wanted to kick Flo's ass."

By emphasizing discounts, Progressive 's perky sales clerk character was apparently getting under the skin of Allstate, the second-largest auto insurer behind State Farm and a client of Leo Burnett, where Ms. Abnee is exec VP. By 2009, Allstate's market share had fallen two straight years to 10.5%, only slightly ahead of Geico (8.21%) and Progressive (7.46%), according to the Insurance Information Institute.

The good-hands people needed their own over-the-top personality to push their message that there is more to insurance than price. "Nobody wants to sit around and talk about car insurance," Ms. Abnee said. "In order to combat that, we needed to entertain. We needed to get people's attention."

Thus was born Mayhem, played by actor Dean Winters, a character that embodies all that can go wrong with your car. Playing a satellite dish, he falls from the roof, crushing a sedan. As a malfunctioning GPS, he sends a driver swerving, crashing into another car.

Allstate got what it wanted: People noticed. And the campaign entered the pop culture, even spawning Halloween costumes. "I saw Mayhem walking down my street trick-or-treating," said Ms. Abnee, a more than 20-year agency veteran, calling the moment a career highlight that gave her chills.

Car insurance -- a $161 billion industry obsessed with risk protection -- is anything but conservative when it comes to marketing these days. The top players are doling out the dollars once reserved for categories like beer and travel, pouring impressively lavish budgets into funding splashy campaigns, partnerships with celebrities and rock bands, Facebook pages and Twitter feeds.

Insurers seem to be slapping their names everywhere. Farmers just agreed to shell out $700 million over 30 years to put its name on a planned NFL stadium in Los Angeles. And the city doesn't even have a team yet.

"This category has gone from a kind of forgotten category to a category with real sizzle," said Jeff Charney, chief marketing officer for Progressive , who proudly boasts that Flo, who debuted in 2008, has helped lure nearly 2.5 million fans to the insurer's Facebook site.

When all lines of insurance are included (some ads plug multiple products) spending for 2009 was $4.15 billion, more than double what the industry spent in 2000, according to industry-reported ad spending figures cited by J.D. Power & Associates that include some direct marketing expenses. That far outpaced the rate of growth for all categories combined, which in that time edged up by just 2.7%, according to ZenithOptimedia.

Not only is the once-staid insurance industry luring top talent -- Mark LaNeve, General Motor Corp.'s former top marketer, left to take the Allstate CMO job in 2009 -- but insurance accounts are now coveted, even cool, at ad agencies. "You're creating brand personality campaigns. What creative doesn't want to be a part of that?" said Dave Schneider, a former account director at DDB who worked on State Farm for several years.

But is the spending sustainable? And how are insurers differentiating themselves in the crowded market? There are no fewer than 11 major TV campaigns on air, running the risk of consumer confusion.

Ad Age talked with top marketers and ad agency execs representing 10 leading insurers. What we found is that no one plans to apply the brakes anytime soon. If anything, insurers believe the way to stand out is to spend more. "We have no indication of a slowdown from a competitive standpoint and we know that we're not going to slow down until we get the job done," said Pam El, VP-marketing at category leader State Farm. "And our job is to capture the hearts and minds [of potential customers]."

State Farm, which has 18.6% of the market with premium revenue of $30.5 billion in 2009, and Allstate are fending off pesky challengers Geico and Progressive , while smaller players such as Liberty Mutual and American Family Insurance are seeking attention with very un-Geico-like serious messages.

Behind it all is an important market dynamic: the shift from the traditional insurance agent to do-it-yourself rate shopping hyped by companies like Geico and Progressive that taught millennials, the 76 million people born between 1977 and 1992 increasingly entering the insurance market, to seek quotes online. Some 48% of millennials turn to the web first, compared with 28% of baby boomers, according to J.D. Power & Associates' 2010 Insurance Shopping Study. Years in the making, this transition is reaching a tipping point, forcing companies that once marketed through agents to make their appeal directly to the consumer.

At first "companies like Progressive and Geico were shaking things up, but many of the traditional carriers essentially wrote them off," said Jeremy Bowler, a senior director at J.D. Power. But "now traditional [agent-model] companies cannot ignore this direct competition. They have to compete on their terms."

The old stalwarts are still finding their way in this new world, experimenting with different messages and even running multiple campaigns at once. State Farm, which last year began running a discount message that sounded a bit like Geico's, is broadening its pitch, hoping to convince young people they still need agents. Other insurers are touting added benefits like emergency roadside service and car replacement.

How can they afford such exorbitant ad outlays? Firstly, companies have emerged from the recession with plenty of profits to help spread their ad messages. Net income in the property/casualty insurance industry reached $26.7 billion in the first nine months of 2010, compared with $16.4 billion a year earlier, according to Insurance Information Institute. Secondly, because it's a mature category, insurers must steal share from each other to grow, experts said. "I see no reason to think [advertising] is going to slow down," said Meyer Shields, an insurance analyst with Stifel Nicolaus.

In many ways you can trace the ad evolution back to one man -- Warren Buffett, who in 1996 made Geico a subsidiary of his Berkshire Hathaway. To this day, Geico Chief Marketing Officer Ted Ward can recite word-for-word what Mr. Buffett told him that year. "You've got a great business model. Everything is working," Mr. Buffett told him and other managers of the then-upstart car-insurance company. "The one thing I don't want you to have stand in your way is money. That's what I've got."

It was a marketer's dream. "I wrote it down," Mr. Ward recalled in a recent interview. Then "I went down and told my folks to start working on plans to become more aggressive and figure out a way to hold him to his word."

That moment would launch an onslaught of advertising the likes of which the car-insurance industry had never seen before -- filled with pigs, cavemen, googly eyes and, of course, a little green lizard that was first conceived on the back of a napkin and debuted in ads in 2000. Geico's gambit of injecting humor into the sleepy and conservative category worked, propelling the insurer to yearly market-share gains and forcing competitors to step up their game. Insurer after insurer is now hitting the airwaves with character-driven campaigns, from "Mayhem" to State Farm's "magic jingle" to Nationwide's "Greatest Spokesperson."

Still, some marketers are learning that humor has its limits -- this is insurance, after all, not beer or soda pop. Just ask Allstate, which was recently forced to retract what was supposed to be a funny press release linking accident rates to zodiac signs. Some customers took it seriously, prompting this clarification: "Astrological signs have absolutely no role in how we base coverage and set rates."

The goal is to grab the attention of consumers who would rather not think about insurance. Experts say most people only ponder policies when they have an accident, buy a new car, move, or renew their existing agreement, which usually happens twice a year. Today there are about 187 million insured privately owned vehicles on the road. Turnover is relatively low from year to year -- 11% of consumers switch their policies while an additional 20% shop but don't switch, according to J.D. Power. But that still means more than 20 million people are in the market each year. And because there isn't much seasonality in the business, thousands of customers are shopping every single day.

Yet the average shopper can name just four insurance brands off the top of their head, according to J.D. Power. And the way to get on that list is to advertise -- all the time. "There's enormous overlap between the companies that advertise a lot and the companies that are growing faster," Mr. Shields said. "It seems very much to work."