I think that many users want to share links with friends. Mozilla noted this recently:
"Perhaps the most common social interaction on the web today is sending someone a link. It's done over IM, email, weblogs, RSS feeds from aggregator sites, bookmark sharing sites like del.icio.us, social networking sites like Facebook or MySpace, and even over the phone. The desire is the same: 'hey, friend, go check out this neat thing and then let's talk about it!'"
Mozilla Wiki -- Labs/The Coop