Being at a VC firm, you get to see a lot of little bits of cool stuff that come together to form a trend or a realization... insight into the big picture.
Last week, Dice ran an ad in Fred's blog with the words, "Does your tech job suck?" In the ad itself was a search box and an action button to generate a job query. They could have created a job search widget and asked Fred to place it on his blog, but instead they just found it easier to figure out what they could monetize a search at, and pay their way into Fred's blog through a functional ad banner.
In the same vein, Brad and I were on a call the other day where we were talking to a VC behind a popular social network making an intro to one of our companies for a business development relationship. However, the company didn't really have a lot of bandwidth to spare for integration, joint development, etc... so the VC just suggested we try and do something in the ad banner space.
Brad called it "self serve business development."
I think as smaller and smaller pieces of code can generate more and more functionality, and sites open up more of their data to powering advertising, you're going to see a lot more functional and interactive advertising show up on websites to the point where you think they're actually part of the site or doing some kind of joint development. The lines between what's a service and what is an ad are definitely blurring.