There are plenty of valid and legal reasons to use P2P file-sharing network, I'll be the first to claim so. But in an objective manner, one can't deny the bad

There are plenty of valid and legal reasons to use P2P file-sharing network, I'll be the first to claim so. But in an objective manner, one can't deny the bad reputation (on the legal side of things) those networks have. And it's pretty easy to understand that Dropbox might not be interested in being related this kind of shenanigans. I also think the Facebook argument doesn't work in the current situation. When you know the risk of being blocked is so obviously high, you don't go and invest 30k$. Facebook have their own rules and somebody who'd be playing on their border should expect and assume the risk of being blocked.