[dllthomas]

You raise an interesting point - that there is a tension between respecting the privacy of a user and making ads most useful to them.

That said, I don't think the rest of your post is well supported. Surely they are using the info to try and target ads, but what prevents them from using it in other ways (including selling it to other people who want to use it in other ways) if they think it can make them more money? Probably, most of these companies aren't going to knowingly sell it to anyone who will use it illegally because they could be culpable... but there are probably things I don't want done to me that don't involve actual illegality. An example off the top of my head might be feeding embarrassing info to a tabloid. And even that stays out of the realm of "what if things really went bad?"