> Also, users can post base64encoded images on a textboard and it's much easier to moderate that sort of thing than an actual picture in plain view.
You bring up an interesting point, which reminded me of the AACS encryption key controversy (09 F9 ...). Take any image, legal or not, and turn it into a huge number or a set of numbers in tabular format. There is nothing illegal about numbers themselves, and the whole thing could easily be seen to just be an array of random numbers.
Even a textual post like this could be considered illegal if the lengths of each word were made so that it could be decoded in some way to "illegal" data. The possibilities are endless and intriguing.