The world's biggest ad spender got some lessons on what digital marketing can do -- and even the downside of digital success -- Thursday at Signal Procter & Gamble, a digital workshop in Cincinnati organized by Federated Media Publishing and drawing much of Silicon Valley's leading executives.

The event, attended by about 500 people from P&G and some other P&G-invited guests, plus another 1,300 webcast viewers, was a first for Federated. It has hosted Signal events for the industry in the past but until now hasn't hosted one for a specific marketer.

By two hours into the event, the #SignalPG hashtag had become a trending topic on Twitter. That lured enough spammers that Federated took down the live Twitter search feed until Twitter CEO Dick Costolo, a speaker at the event, helped get the spam canned.

While there was little big news, the bigger takeaway for marketers may be the strong endorsements for digital marketing that P&G Chairman-CEO Bob McDonald and Global Brand-Building Officer Marc Pritchard gave from the dais.

Mr. McDonald, who has of late talked much about the potential for digital marketing to help P&G save money, also discussed the power of digital to make marketing better. Responding to a question -- really more of a complaint -- from a marketer for P&G's Venus brand about the restrictive nature of P&G's privacy policies, Mr. McDonald said the opt-in nature of social-media programs helps instill a new incentive to create "big ideas" that get consumers to voluntarily engage.

P&G's internal surveys still suggest employees see the company as too bureaucratic and hierarchical, Mr. McDonald said, but it's been trimming management ranks in part to address that .

One goal is speed in digital and elsewhere, he said, noting a 24-hour turnaround on a MyTide video and 15-second TV ad showing use of the detergent to clean up a jet-fuel spill following an accident at the Daytona 500.

"As a brand builder, you have to take advantage of that ," Mr. McDonald said. "You can't be mired in this plan you put together in the Kremlin."

But, he added, "I feel like we're in the early innings" in digital marketing, in part because "it took us some time to get the right leaders in place, like [Global Brand-Building Officer] Marc Pritchard."

Mr. Pritchard pushed P&G's recent digital-is -more-efficient strategy, saying digital and public relations give P&G the greatest return on investment and "go hand in hand."

Digital-media vendors took the cue in presentations that ranged from subtle to overt plays for bigger pieces of P&G's $9.3 billion annual media budget.

One of the more aggressive -- and data-filled -- pitches came from an increasingly important P&G retail customer: Amazon. Lisa Utzschneider, global VP-advertising sales for Amazon, revealed results from a campaign last year that involved an ad for a $10-off online deal for Crest Whitestrips on Amazon. It produced a 26% lift in sales for Whitestrips on Amazon, she said, but, more interestingly, an 8% lift in offline sales, representing $1 million in incremental sales.

"Think about that promotion," she said. "It's 10% off on Amazon. You can't redeem that off of Amazon. Yet customers responded to this message, and we love the ROI we saw offline."

Those results are similar to what Amazon is seeing for other CPG advertisers as it increasingly uses marketing-mix models to evaluate the offline impact of ads on its site, she said.

Only 4% of Amazon shoppers are buying CPG products today, Ms. Utzschneider said, calling it "day one in the CPG category" -- like it was for other goods in 1997. But that 's not stopping Amazon, she said, "in moving further and further up the funnel and connecting with customers."

Twitter's Mr. Costolo said P&G was one of the first users of sponsored Tweets, despite recent media reports suggesting meager spending by the likes of P&G was an impediment to its revenue prospects. Among the earliest and most successful uses of Promoted Tweets was the one that pushed the Old Spice "Responses" campaign in 2010.

"Our revenues are the last thing I worry about," Mr. Costolo said in a Q&A with Federated Exec-Chairman John Batelle. "The business is growing exceptionally well."

Digital is helping transform P&G market research, too, said Nick Nyhan, chief digital officer of WPP's Kantar. After extensive testing of various social-media metrics against conventional metrics, P&G found the strongest correlation between Twitter volume and purchase consideration via the survey-based brand-tracker P&G uses, he said.

"We drilled down and found a good leading indicator," Mr. Nyhan said.

Mr. Pritchard said he'd spent the day writing down "a list of applications our brands can and should be doing for every speaker. And I hope everyone did that ."

He said marketers should stop asking themselves "what is the P&G way" and urged them to listen to their gut feelings. "You're not going to get your head cut off for trying things.

"We're doing things like this because we want everyone to know we are open for business" on digital marketing, Mr. Pritchard said, noting that P&G had worked with Federated to put the summit together in less than seven weeks.