Perhaps we can have a Buddy list system? Whereby friends of a user are displayed in his/her profile. Adding of other users in their buddy list would also require approval from them.
I would love to see at least the buddy list in the profile. Approval is optional.. :) It would be nice to see that sort of connection along with the profile comment mod this could be really cool..!
This sounds more like a cool thing for a mod than a feature which any SMF board should be having. And it just happenes it already (sort of) exists (http://custom.simplemachines.org/mods/index.php?mod=58).