That's just ridiculous. Nobody reads user agreements, everybody knows nobody reads user agreements, and pretty much everybody expects that if you purchase something through a company, that company is responsible for delivering.

You can't reasonably set up a marketplace, be the middleman for buying and selling, then throw up your hands and say "sucks to be you" when the product you advertise doesn't get delivered to buyers.

This might be legal, but it is completely nuts, and the existence of a "we're completely nuts" clause in the user agreement doesn't mitigate that.