I just doublechecked; I'm not aware of ever having gotten out-and-out spam from them. You can choose to get comment reply notifications, etc., but you can also turn that stuff off. So the service itself is 100%. As for privacy, they hash your email address to use as the placeholder ID for non-registered users, so it's fairly secure (plus, you can go back and claim any comments since they've stored the hash, which is kinda cool. I had several show up in my account that I'd forgotten about making when I registered.)

Note: if you comment at a site using Disqus, the site owner does see the email you registered with. But that's pretty much the case w/ any commenting software. And that only works for people who have actually commented at the site (kenzoid.com, in my case); I can't just go surfing around the disqus userbase sucking up emails just b/c I use it for comments. It does link your comments together, of course, but that's kinda the point. *grin*

I dig it...I had an account before I used it on my site, and it's been pretty much flawless through two different site backends now. Recommended as both a commenter and as an admin.