I have been aware of MySpace for a number of years and even created an account a few years back simply to stay in touch with one particular friend. I have never been a big fan of MySpace - the layout is just not to my taste, but I do appreciate the attraction for those looking to reconnect or make new 'friends'.
I can see why a library or school would benefit from a presence on MySpace - especially at secondary level. It's just another tool that could be used to connect with students (especially teenagers/young adults) on a level and platform that they are familiar and comfortable with.
Certainly would not recommend for primary level - but for that matter most schools would have sites such as these blocked (or so I would hope).