On the plus side, kudos to them for even taking a stab at this. I mean, many companies have been doing this, and I can't remember any that provide granular user control like this. (Indeed, most try very hard to pretend they don't exist.) For people who would like their advertisements to at least be interesting and relevant -- and yes, I'm pretty sure there are such people -- this actually looks rather useful.
That said, they do lose half a point for the sheer obscurity of this page. I'm curious: how many people here knew the page existed? I'm pretty sure I hadn't come across it before, and I'm moderately well-read in the field. I can certainly understand their incentive to not push it into peoples' faces too much, but it does illustrate the difference between "Don't be evil" and "Be good" -- there's a degree to which commercial interest hinders them from being *too* actively good.
Still, I'm glad to see it, as well as their link to the Network Advertising Initiative Behavioural Advertising Opt-Out Page -- a nice one-stop shop that lists a bunch of co-operating ad networks, shows which ones are doing behavioural tracking on you (again, presumably just for this browser), and lets you opt out of them individually or all at once.
Truth to tell, I'm relatively blase about the topic: I deliberately live my online life fairly publicly. But I know that a lot of folks care about it, often with very good reason, so this is a helpful way to claw back just a bit of your online privacy...