And with the crazy odds on the flop and the free card, it's easy to back into it.

I definantly fold preflop, and I raise the river. Remember the goal of betting the river... either to make a better hand fold, or a worse hand call. You're clearly not making any better hands fold, and if someone has one, you're paying them 2 bets.

So are there enough hands that will pay you here to outweigh the flush and the boat costing you an extra bet? Sure there are... 3 broadway cards leads to LOTS of two pair/high pair situations. Very rarely is someone going to fold for one bet here with a decent hand, so you know you'll get paid if the better has anything, and you'll usually get a call or two from the other players as well.

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-You may not know this, but poker is a game of incomplete information.