Bob,
That is a good question. I was thinking in terms of building a brand or driving traffic. If you are looking for SE improvement, then you are in the backlinks crowd. I think MySpace allows "follow" backlinks within posts and things. So it would most likely be favorable to befriend users with high ranking (
PR) profile pages and commnet with backlinks. Like
http://www.myspace.com/foxdeluxe is only a PR1, but a backlink is a backlink.
::BUT::
Beware the potential SE Algo update that negates backlinks on spammed out social sites like squidoo and MySpace.[/code]