Good question indeed. My opinion is to not do it, if people like your shit, they'll buy it. If they haven't even heard of it, they'll find it. Let the people come to you, don't go to the people. That's how you get a lot of fans calling you arrogant / cocky, or they want you to back down. But, then again, there is a crap load of artists out there, that if they have your e-mail, or you have them added on MySpace or something, you get about 50 comments a day about their songs, or something like that.
Do as you wish, and what you think will get _you_ where you want to be. If that's spamming e-mail inboxs, then so be it. Just don't do it to mine, because I'll hit you back, only with a flood.

jk.
As always, be cool.
--Re-Lapse