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.
Honestly, a more scarier concern is that there is likely to various illegal things posted on this as soon as enough people get on it.
Awesome! As long as you're monitoring it. Keep this going!
So how many of the images that have been linked to are child porn?