I already find tons of stuff I didn't know on Google! More, seriously, advertisers already "target" ads based on such loose parameters as age or location. Let me set my age as a filter if I want to, then you can show me those ads. Pinterest is starting to monetize people browsing semi-aimlessly through pages of tangentially-related items. This could just be a variation on that.

Actually, with Google, advertisers don't target anyone, really. They have a few knobs to tweak, but mostly it's Google that does the targeting, based on much smarter (but not yet smart enough) algorithms.

So, you must correlate advertisers.

But it's hard to design something that can not be gamed. As a user, there's no reason to adopt the more obvious possible solutions, because I wouldn't be able to verify that I'm not being tracked. (What means that I'd adblock it like any other source, and thus there's no reason for the site owner to use this one service.)

Are you implying ads is the only way to know about products and ideas ?

very true-did not think about this-good point