I actually don't think this is all that bad. (I'm not sure if it would be enforceable---the classic common law rule is that liquidated damages clauses have to

I actually don't think this is all that bad. (I'm not sure if it would be enforceable---the classic common law rule is that liquidated damages clauses have to actually be a genuine estimate of the party's damages, not punitive... but it's also been a while since I've done contract law.) It seems like the defense of this is fairly simple. (1) People ought not to be able to use their matchmaking services without giving them a cut, that's shitty, and why not use contracts to enforce it---just the same as other kinds of matchmaking services, like job placement agencies, do. (2) Also, it's probably safer for consumers to use their platform to have things like built-in verification of transactions, maybe(?) insurance(?) etc. anyway. Same reason it's a bad idea to take the AirBnB or Ebay or whomever transaction off-platform, because that's how crooks siphon away recourse for their frauds. So why not use a little bit of coercion for everyone's good?