Comment spam has always been a problem at this site, even though I used the drupal recaptcha module to fight it. Some days ago, it escalated to a point where I couldn't keep up moderating the incoming spam comments. So I started looking at comment systems, and ended up with comparing DISQUS with Livefyre. They seemed quite similar but Livefyre didn't have any Drupal module so I chose DISQUS. Since I installed it, I haven't received a single spam comment. Lots of time saved for me and more fancy features for the commenters.