How You Choose Your Friends

An interesting study showed that proximity, rather than shared interest, better promotes friendship. Basically, you are more likely to become friends with the people your are stuck sharing a space with, like neighbors and workplaces, than you are with people you aren't forced to be around all the time, but share many more similar interests.

This is interesting in creating friendships in online communities. Forcing people to work within close quarters is more likely to produce online friends. More online friends = more stickiness for your social site or MMO. Therefore, having mechanics, such as required groups for completion of raids or battlefields, foster more stickiness than allowing people to search for, say, other cat lovers.