If, like me, you enjoy checking email while driving, it should come as no surprise that our compulsive multimedia-multitasking tendencies also extend to Web/TV cross-pollination, according to Harris Interactive’s latest study. Nothing particularly revealing about the first two items in this chart: you mean to say TV doesn’t fully occupy our brains? Stunning.

But the third item — the 19% related content surfing — now that’s interesting. In these cases, I think the Web is often providing a gloss or a deep-dive on TV content. You’re watching “John Adams” on HBO and can’t keep your Founders straight? It’s Wikipedia time.

As online media becomes more micro-targeted and contextual, this cross-pollination offers huge potential. Big brands spend billions trying to drive from TV ads straight to the Web, with limited success. Why? Because that would be counter-contextual: you’re not watching TV for the ads, you’re watching for the content. What if instead of buying all that TV time, marketers purchased related search terms and placed ads on relevant content sites only during key programming?

Example: there’s a show on Nat’l Geo about Greece. Your cruise line offers cruises to Greece. Instead of buying advertising during the show, you bet big on Greece-related keywords and display ads on related content sites only during and after the show. Ad-serving technology finally makes this level of dayparting possible. Think of how much efficiency you’d gain over a big offline buy. Has anyone tried this? I would love to hear how it went.