I think they have a pretty strong anti-censorship stance, and due to the way the data is en/decrypted on the client side, they have no visibility what the data consists of.

On top of that, the data here (which is posted with the mega.co.nz decryption keys standard as part of the URL) has an additional layer of encryption by the uploader, so for all anyone can prove it's pictures of cats, and not anything illegal.

It looks like mega.nz has now removed them.