While it's a good idea in theory, it would ultimately fail if we tried to apply it to reality. Think about it. Ignoring the fact that we are releasing personal information (no matter how trivial), attached to our email address, how often do you personally recieve spam that is useful or interesting to you? If the answer to that question was anything other than "never", guess what? It wasn't spam. Spam emails are mass emails that generally want you to click on their link. This will most likely direct you to their site, ask you to complete other offers, populate your screen with popups, etc etc etc. Perhaps some people like completing 5 offers which cost them X amount of money, in order to recieve an Xbox six months later. Perhaps some people like being asked if their breasts need to be twice as big. Perhaps some people like their computer crashing repeatedly because of a virus they've infected their computer with by opening an email, going through a link, or downloading an attachment. Personally, I am none of these people. Spam is classified as such for a reason. They are emails that we don't want, and don't ask for, the internet version of junk mail--only without the tiny bit of irritation that comes with getting the latter, thinking of all the better things someone could have done with the millions spent sending out glossy paper that immediately goes in the trash. Either way, regardless of whether or not I personally like spam emails, someone has already implemented the idea of sending people advertising emails based on what they like: mailing lists.