The only way to effectively use myspace for promotion (unless you happen to already have a built in fan base, like a major recording artist, or whatever) is to be a "friend whore"
Spend hours upon hours every day friend requesting everyone, until you too have as many friends as the illustrious 'Tom' Then, when you send out bulletins, everyone gets 'em, and so long as you write compelling copy, you could generate some worthwhile traffic.
Aside from that, it's wholly overrun by obnoxious teens, and (I hate the term, but it seems to be an accepted part of the lexicon now) "tweens" or worse yet, "tweens" pretending to be teens, and worse still dirty old men pretending to be teens.. and so on and so forth.
A viable BUSINESS promotional tool, nah, probably not.. a promotional tool to pimp yourself out to the reality-tv-instead-of-REAL-MTV generation, yeah.. it's probably good for that.