> Well, you are privately allowed to bet on whatever you like with another individual.

What jurisdiction are we painting with that broad brush? This is far from universally true, even in the US.

Nope. "We're just an intermediary between people" is a 100+ year old yarn that casinos and bookies have been trying to spin. If you're presenting a point of entry to a betting line and taking a cut, congrats, you're the house. Doesn't matter if you adjust the betting line manually based on intuition or algorithmically based on betting volume. Sometimes it doesn't get enforced because of corruption, but if this was the case, then why aren't there tons of independent unregulated poker casinos where players just play against each other? If you facilitate and take a cut, you're the house.

Can you name the individuals you are betting with on Polymarket? Can they name you?

That "facilitating" argument didn't work out for Silk Road.

What the hell are you talking about? You are absolutely not allowed to bet on whatever you'd like with another individual. Depending on what you're betting on (for example, the price of a stock or the throw of a card), it falls under varying different regimes. This is highly regulated and has been for most of the whole of human history.

Yes, there are de minimis exceptions. Your office NCAA pool, for example, is often legal, but it has nothing to do with what we're talking about and is also irrelevant to a business facilitating it via 18 U.S.C. § 1955.