An early milestone for Twitter came back in 2007, when tweets-per-day tripled virtually overnight -- to 60,000 from 20,000 -- thanks to it becoming the flavor of the week at the South by Southwest Interactive conference in Austin, Texas.

Fast forward five years, and those numbers sound kind of adorable. Earlier this month, during the final-night telecast of the Democratic National Convention, chatter about President Barack Obama's speech alone drove up to 52,757 tweets per minute, a new record. (A week earlier, Mitt Romney clocked in at a peak of 14,289 TPM during his speech.) Overall, the 90 minutes of the convention that aired in prime time that night inspired more than 2.5 million tweets.

At Advertising Age, we've been reporting on the so-called social-TV phenomenon since before it even had a name, thanks to editorial partnerships with social-media-monitoring firms, including New York-based Trendrr, a relationship that goes back to the summer of 2009. That's when we began to understand one of the great ironies of the growth of Twitter and social media in general: TV is what people want to talk about a lot of the time, particularly good old-fashioned prime-time TV.

Now we've got a multimillion-dollar social-TV industry, including an exploding metrics sector with plenty of new competition for Trendrr (most notably Bluefin Labs, another Ad Age editorial partner) and dozens of startups creating consumer-facing apps and services.

But beyond the B2B, back-end and app companies, who's actually making money off social TV where it really counts -- at the network level? What does it take to monetize social? Some answers:

Social TV can make for bigger deals and incremental revenue

Over the past year, as Nielsen has released research that correlates rising social buzz with increases in ratings , there's been plenty of debate of the chicken-and-egg variety. But the London Olympics helped convert a lot of skeptics.

"It was a really bright, shining example of how social could fuel ratings ," said Peter Naylor, NBC Universal's exec VP-digital media sales. "People were really, really concerned about social being a spoiler, but it actually worked as an accelerant, and when we sold advertising packages, we made sure that for all the windows, all the platforms" -- most notably the NBC Olympics Live Extra app, which offered live streams of more than 3,500 hours of content -- "we associated marketers with those platforms."

But the point, said Mr. Naylor, was to drive higher-cost cross-media deals, not stand-alone digital deals. "We are not really interested in selling digital adjacencies unless they've bought the core [broadcast] property. We had 30 advertisers on the Olympics digital platforms, and 30 out of 30 were TV advertisers. If an advertiser says, "We're not buying the core show, but we want to buy the digital execution,' that 's not going to happen because we continue to put the marketers' needs first and we know that broadcast and social work better together."

Social TV drives real traffic

The chicken-and-egg argument about social driving ratings or vice versa might go on forever, but for CBS Interactive sites, including CBS.com, TV.com and Clicker.com, there's really no debate. "As we push stuff onto Twitter and Facebook -- a clip or a photo or a comment made by talent from one of our shows -- we can see that large portions of the traffic to our sites are being driven by leads generated that way," said Marc DeBevoise, senior VP-general manager at CBS Interactive. "And, of course, more traffic to our sites drives more revenue."

That social-media-driven revenue has been growing all year: In February, for instance, CBS signed Target and GM to sponsor its three days of pre-show online coverage leading up to the Grammys telecast; this summer, Microsoft's Skype unit was the launch sponsor of CBS Connect, the Facebook- and Twitter-integrated social hub for all of the network's shows; and AT&T just backed "Fall Preview Plus ," a second-screen companion program for the annual "CBS Fall Preview" prime-time special.

Engagement research is helping drive home the value of social-TV initiatives

"I think that layering in dedicated social-TV opportunities allows us to get closer to the desired consumer," said Kirsten Atkinson, media director, Team One, which works with Lexus. "For instance, USA Network is one of the most social networks, and "Suits' is one of the top five shows on cable right now in terms of drawing affluent consumers" -- facts that helped clinch Lexus sponsorship of both the show and its social-gamification program, "Suits Recruits."

"We put together a custom brand study that looks at some core Lexus attributes and how we've moved the needle with initiatives like "Suits Recruits,' because ultimately the only way that we know that we're getting this audience closer to a purchase is gauging how they feel and think about the brand," said Ms. Atkinson. One thing Lexus has been achieving with its social-TV initiatives, said USA Network SVP-Digital Jesse Redniss, is sharpening its reputation in a key area: "Lexus focuses on technological innovation in their brand positioning, and "Suits Recruits' not only showcased their cars" -- the show's actors shot web-exclusive scenes incorporating Lexus vehicles -- "but exemplified the fact that Lexus stands for innovation," Mr. Redniss said.

High engagement is pulling in sponsors who need . . . high engagement

Some shows are more inherently social than others, and the same is true with advertisers. For instance, credit-and-charge-card marketers are big on campaigns that emphasize friends, families and community. "We did this great partnership," said David Wertheimer, president of digital at Fox, "with American Express around "Glee' to promote their Members Project campaign" -- a feel-good charitable initiative with the tagline "Everyone can help change the world for the better, one step at a time."

The season-long campaign not only leveraged off the show's social buzz, but, said Mr. Wertheimer, "We were able to get the cast of "Glee' to take part and we used the social-media presence of the "Glee' characters like Mr. Schuester to promote this idea of doing good, and Sue Sylvester, obviously on the other side of that , poking fun at do-gooders."

Mr. Wertheimer said that the fact that Fox showrunners and stars are increasingly social-media natives -- such as Zooey Deschanel (3 million Twitter followers) of returning hit "New Girl" and Mindy Kaling (1.9 million) of the upcoming "The Mindy Project" -- means that "the talent" increasingly gets the value of social-TV initiatives. Samsung and Pepsi have been among the sponsors of tweet-worthy "Video Extra" clips for both shows at Fox.com.

Social TV is creating new opportunities for brand integrations

Even smaller networks can leverage social media to move the needle, said Greg Kahn, exec VP-business development director at Optimedia: "With "The Walking Dead' in particular, I think AMC has done a terrific job with social TV. I think a lot of their shows have outperformed the norm because of social, and that social success has extended to the advertisers as well," he said.

Hyundai, for instance, sponsored the Walking Dead Elantra GT Sweepstakes, and the introduction of the Hyundai ZSM (Zombie Survival Machine), at Comic-Con this summer. A concept-car collaboration with Robert Kirkman, the creator of the "Walking Dead" comic books, the tweet-ready ZSM (available in only one finish: matte slate gray) included an armored-roof hatch and hubcaps equipped with protruding blades. Even the tongue-in-(bloody)-cheek URL for the initiative -- HyundaiUndead.com -- suggests that social strategies in TV land are alive and well.