A couple months ago, Nature had an article on using social networks to filter spam. The basic idea is that people tend to send mail to people whom they know, and the system could induce users’ social networks from message headers, and detect spam because the messages aren’t sent within a social network. If you’ve already got social network software and email, why bother inducing the social network? Why not just integrate the two, and make an automatic spam whitelist? Google is in a position to do just that, with GMail, its impending free email service, and Orkut, its social network software. That might actually give me a reason to join Orkut.