Hi misterdonman, good seeing you again!
There have reportedly been lawsuits against affiliate networks for letting affiliates promote on MySpace, so lots of networks prohibit it.
See this article:
Myspace 500 Million Lawsuit Against 20 Ad and Affiliate Networks
More and more affiliate programs and networks (including Amazon) now only allow you to drive traffic that comes from your own site and don't allow Twitter, Facebook, Myspace or other social network traffic.
So you need to check the TOS for each affiliate program.
Hope this helps and best of luck!