On some blogs yes. Most comments are spam, if you have a filter turned on like Askimet you'll find there's not very many comments to moderate.
Most of the comments on
http://www.funnypornvids.com/ are from me but it's new so only gets 270/day. So don't worry about having to heavily moderate your new blog. Like Walrus said you might get 1 comment a month on a porn blog.