MySpace seems to be a growing problem, its alot easier to block the usage of it a a corporate level, which we had to do.
I basically told my firewall to look for all URLs that contained the words "myspace" in it, and have it reject it.
I got a alot of hate mail from my users.. but I told them that they should not be using MySpace on company time.
Some personal firewalls may be able to do this, though I am not sure which ones, but one might try simply putting this as a URL block:
*.myspace.com
That may work instead of trying to figure out all their IPs, and hostnames.
Now this only works for hostnames... but as soon as I figure out what ranges of IPS they use I am going to create IP Routes on my internal internet router to route back back to 127.0.0.1.
But for right now its working... though my rule in the firewall I have does prevent them from doing a ping, nslookup, etc.. again because its looking for any content that contains myspace in it.