If you're the average person, I don't think this hurts. I'd rather see relevant ads than random bullshit. Heck, even I click ads when I think the referred site will help me.
If you've got something to hide or have "privacy" issues than browse Incognito. Otherwise, I don't see how it matters much. More targeted advertising... makes sense for advertisers, consumers and google alike.
BTW I think Chrome will help FireFox AND Chrome both flourish and take away from IE's stranglehold. Not only that, but perhaps spawn completely new browsers.