Anyone can comment on a Disqus blog post. They don’t have to sign up for your blog. They don’t need to give you their email address. They’re already a member of Disqus. As a reader, I like it because it makes it really easy to leave comments. As a blogger, I don’t mind it if it leads to more engagement and a larger audience and more attention—I’m willing to give up any potential ownership of comments or anything like that.