Ah yes, crowd-source-able humor! Now I'm even more impressed. 53 sites is a lot. Do you have people that oversee the content & comments on those sites?
Yes. We have a lot of people overseeing content and comments, it's most of our staff. Each person generally does between 4 and 6 sites, with the sites generally posting between 1 and 6 items to the front page (featured content) daily.
For each thing you see on any front page, there are dozens of things that didn't make it through voting, and for each of those things on the voting pages, there are dozens of things that weren't good enough for voting. We're able to crowdsource the generation/submission of content as well as (some of) the curation of content. A lot of what makes a site work is finding the right balance between editorial vision and letting users vote on what they like.
FYI for anyone else who is curious like I am about what those 53 sites might be: http://cheezburger.com/sites