Social software with a 'how closely I'm related to you' feature would be compelling. Social networks obviously apply, but how about when you exchange emails wit

Social software with a 'how closely I'm related to you' feature would be compelling. Social networks obviously apply, but how about when you exchange emails with someone... wouldn't it be cool if it mentioned a common ancestor in the footer? Oh, and on a dating site, automatically filter out all first and second cousins!