Not legal per se, but my Venmo was frozen and now closed which sucks, because I use it for a lot of vanilla things.
I did use it to send money to a sugarbaby and once to a provider for $50, but that was almost a year ago.
So, part cautionary tale, and part seeing if anyone else had this happen.
I'm assuming this is why I lost my account. There's a lot of ways to violate the user agreement on there. They don't tell you why it's terminated and they don't offer an appeal process.