I haven't had direct monetary success using MySpace to advertise anything in quite some time, but it might be helpful to remember that PR is not the only thing that matters. If, as many people believe, SE's like Google are using LSI as one part of their indexing algorithms, creating semantic "neighborhoods" by associating a series of words together with a specific site may indeed be helpful, though I imagine the fact that you're doing it on MySpace would all but negate the positive effect.
To answer your question simply, I would abandon it unless you're able to do bulk edits, because you could probably be using your time, resources, and energy in a far more productive way. Hopefully that was helpful.
Regards,
oldenstylehats