Recently, though, an accelerating trend has led to new challenges for those looking to support their digital media through advertising: Marketers are increasingly taking what used to be above-the-line dollars and placing them into the media they're producing themselves. They are using marketing funds to attract their own audiences, rather than advertising to others'.

PepsiCo, which spends many millions of dollars on marketing every year, is just one example. During Internet Week in New York, I helped lead a project for which we hired nine "social communicators" (some of whom were traditional journalists) and built out a suite of blogs and social media tools, including a Twitter feed, a YouTube channel and a proprietary app, to cover the week's events and, PepsiCo hoped, reach an audience of influential people in digital media and marketing. PepsiCo has done similar projects for the SXSW festival and said it is planning more in the future.