It's true. Let me tell you about this true example that happened when I was playing on Friday night:
It's the baby game, and I've amassed a stack of ~$1500 in (play) chips. With such a large stack comparative to the table, I turn from "only monsters" princess into G-Rob "how much do you really like your hand, short stack?" princess. I'm in the cut-off (ish), and see J9 of clubs, and since it's folded to me, I bump it up to $15 to play. The guy to my left calls, because he calls everything, the button folds, the SB folds, and the BB calls. $47 in the pot.
Flop comes down Ad Jx 6d. BB checks, I decide to check, the guy behind me checks, and the check is good. $47 in the pot.
Turn is a 8c. BB checks, I bet $30, guy to my left drops, BB agonizes yet calls. $107 in the pot, heads up. I put the BB on a flush draw at this point.
River is another 6. BB goes into the tank and starts thinking. After about 10 seconds, I say "that's not a diamond, sweetie", at which point he makes a hand motion and mumbles something. I take this as a check, as does the dealer, and I turn my hand face up, as there's NO WAY I'm going to bother betting that with an ace and a pair on board.
The BB looks at my hand and then pitches his cards to the dealer at which point she pushes the pot towards me.
Of course, at this point, all hell breaks loose, and the BB starts screaming that he actually said "ALL-IN" not check! I told him I didn't hear that and the dealer concurred, and he mucked his hand. Instead of getting into a shouting match, I told the dealer to call the floor and let them make the ruling.
We explained the story to the floor, and the BB INSISTED that my hand was dead because I tabled (showed) it. This is true if there are more than two players in the hand, however if you are heads up, you can expose your cards all you like, so my hand was still live. The guy was not happy when the floor explained that to him, too.
The floor agreed with me, and awarded me the pot, to his screams of "but I folded trip SIXES". The floor said that the only hand he saw at the table was mine, and he couldn't prove he had trip sixes, and thus, I was awarded the pot.
In fact, said the floor, I was being extremely nice because if I'd wanted to - as soon as I realized that he said "all in" and then mucked his hand, I could have said "call" and had the rest of the chips in front of him.
Somehow the BB wasn't mollified by that. In fact, he then began to say that he was going to call all my $30 raises and get his money back.
Sho'nuf, 3 or 4 hands later I see Serena and Venus and raise to $30, and he (and the guy on my left who calls everything) calls. The flop comes down 9 7 2 all spades, and he checks to me and I bet $75; I don't LIKE the flush on board, but since I've got the queen of spades, I'm going to bet this pretty hard.
The guy who calls every preflop raise folds, and sho'nuf, the BB pushes all his chips in. Since it's another $20 to me, this is an easy call.
... imagine my surprise when he turns up a monster: 8s 3h. SHIP IT TO ME.
So, kids, here are your lessons learned:
1. You can expose your hand to your opponent when you're heads up
2. DON'T give your (winning) cards to the dealer until you have been awarded the pot
3. 8s 3h is rarely worth $30 preflop, and not so much after a flop when you're drawing to a 9 high 4 flush.