[lowndsy]

Very powerful, and while it could concern potent demographic data, it's also fairly anonymous, so they could probably get clearance to do it. Since the ads (whatever they turn out to be) would probably be integtrated into a client site adsense style, and probably won't actually integrate with the client site much, it could be argued that the demographic data isn't actually being given out. I would imagine the cookie will contain a machine readable string of values which aren't much use to anyone except an ad script.

What worries me is, if they're using cookies, What is to stop other sites / applications which have nothing to do with the facebook scheme reading or altering that same cookie? You can be sure that even if the cookie is encrypted, some 4 year old will crack it within a few minutes of it being released, and while it won't tell us sensitive things like names, or even ages, if facebook can use it then the data could well be useful to *any* ad network.