It depends on how much money there's to be made, just like every other counter-abuse measure. Proof of work is useful for protecting things worth like a thousa

It depends on how much money there's to be made, just like every other counter-abuse measure. Proof of work is useful for protecting things worth like a thousandth of a cent per transaction. Captchas for something worth 1/10th of a cent. Phone number verification for something worth $0.1-$1. Real-world presence and real-world id checks for things worth $100. The amount of money you can make scalping tickets is way higher than that, so it's not a useful defense. Doubly so when the cost of the phone verification isn't even per-transaction, but once per account. For the ticketmaster case, I think what you'd want is some kind of proof of stable liveness at every transaction. It's easy enough to game proof of liveness, or proof of unique identity, at account creation time. Just the classic method of paying people at a parking lot $5 to pass a "wave to the webcam" captcha. But they can't get those same people back for another captcha every time they want to use that account for another ticket. (Though it's possible that deepfakes have rendered webcam captchas effectively worthless in the last year or two, I don't know where the state of the art on deepfake detection for this kind of usecase is.)