It might be a nice feature...on the other hand...it could become an issue much like Face-Book where the whole point is to gather as many friends as possible.
Sometimes it's better to keep friends discrete, if one person your friends with isn't friends with another one of your friends...it might cause problems.
Cause with the level system...it's all about who's on top. Who's the top five or the #1 vs the bottom of the list.
And EVERYONE....will be asking famous artist with COUNTLESS numbers of PM messages asking to be part of their friends list...making one upset if it is turned down.
It might be a good idea...but it might not....depending on certain situations like the one I mentioned above.