Very, very interesting...<p>I think it would be a good idea to keep the actual location data inaccessible to the end user, but I can imagine it fitting in well with a site like OkCupid.com. OkC currently has a feature that parses profiles for relatively unique words and points out that you and the profile you're looking at share an interest in X (maybe a movie title, or a book, or an activity).<p>I imagine an interesting implementation being "this user also frequently visits Starbucks on 6th Ave" as an ice-breaking feature along with the match recommendation system.