Good question and it's definitely a concern. For now, I'm just monitoring things manually, but certainly would need a more scalable system if the site grows.
Or worse like paste in, Bitcoin and other public places people will post urls to terrible/illegal things on the internet. People always find a way to ruin the public commons.
Not really related, but I just browsed through all the projects on http://unfoundedlabs.com/ and really enjoyed it. You have a unique voice and an artists sensibilities which will now serve as an inspiration to me.
Just a warning that there might be some NSFW content on the websites. The very first site I opened (the one about a collaboration on shirts or similar) has a half naked woman in the first picture.
It also supports img tags. Being able to write HTML is very powerful. Markdown support would just add feature bloat. Next you will ask for a markdown live preview.