When it initially launched, I saw Satisifaction as an incredibly brilliant idea that was equally well executed, but I didn't really get into it. Recently, as I was trying to make a decision about setting up forums for Next Update...
http://nextupdate.com/blog/archives/2008/04/getting-satisfaction/We'll only send emails for significant product announcements, and those happen every couple of months at most. Of course, we won't give away or sell your e-mail address either.