I didn't know you could do this so I thought I'd let you guys know about it in case you didn't know either..
I wanted to play GT5 remote races with a mate at work - so we added each other on Facebook, made sure we both have the PlayStation Network Facebook app enabled (http://apps.facebook.com/playstation/).
Then you can go to the Friends section and it'll list your Facebook friends who have the app on their profile, and from there you can add each other. If you both add each other then it counts as being a mutual friend request and you don't even need to go to your PS3 to accept!
Handy in a situation like this where you can't get to your PS3..
I wanted to play GT5 remote races with a mate at work - so we added each other on Facebook, made sure we both have the PlayStation Network Facebook app enabled (http://apps.facebook.com/playstation/).
Then you can go to the Friends section and it'll list your Facebook friends who have the app on their profile, and from there you can add each other. If you both add each other then it counts as being a mutual friend request and you don't even need to go to your PS3 to accept!
Handy in a situation like this where you can't get to your PS3..