Online content can target ads individually! I've filled out the survey on Hulu, they know that I'm a guy, my age, etc. They probably have pretty good guesses about my income and my interests. The full set of shows that I watch paints a pretty detailed picture of who I am and what I like. In an ideal world, they could use that information to show me very precisely targeted ads.
That famous quote, "Half the money I spend on advertising is wasted; the trouble is I don't know which half." is probably mostly right, except I'd bet that it's a lot more than half that gets wasted. And Hulu should have the ability to fix that, by individually targeting ads! But they're still showing me, a fairly nerdy guy, lots of Febreze ads and Glade sense & spray ads and even the occasional tampon ad or whatever.
Google is proof that precisely targeted ads are really, really valuable. And I think targeting ads well even makes them less annoying; if you're showing me something that's actually relevant to me, I feel less like my time is being wasted. But Hulu and its advertisers still haven't figured out how to match up ads and users.
It's sad. But whoever actually solves this problem will make oodles of money.