The Most Common Mistake

What's the most common mistake you see players make online?

I know there are a lot of possible answers to this question, but the mistake I see most commonly, and this is probably just because I see it so often, maybe 20-30 times per hour, is doubling the blind in a NL/PL game.

$25 NL game on Party Poker. I'm on the BB with 92o. UTG raises from $.50 to $1.00. Three other players call. It costs me $.50 to get into a $5 pot. Even 92o is good in a 10 to 1 action. Flop is T95 rainbow. It checks to me, and I check with my pair of nines, no kicker. Turn card is a deuce. UTG goes all in. I'm thinking "did UTG just catch trip deuces?" One caller in front of me and I call all-in since UTG has me covered. River is a rag and the caller flips Q9 and UTG has....AA of course.

I cannot come up with ONE situation where that raise is a good move. It doesn't accomplish anything. It builds the pot a little. But the only way it can build the pot is if you get a lot of callers. And why do you want to face a lot of callers with a pair? You are forcing your AA to catch a set if you want to win. That's like playing AA the same as 22. Insanity. How many 5 way pots do you see that are won by a pair? Not many. There's a world of straights and flushes waiting to knock your pair out. But heads up? Small pairs win all the time.

A few hands before this I get AA and raise to $4. I get one caller with A8o and I win a $48 pot. I raised to isolate, got my one "sucker" and took him down. So I even showed this moron how to play his AA and he didn't pay any attention. The beauty of Party Poker is that you will ALWAYS get a sucker to call your pre-flop raise, and the other beautiful thing about Party is the suckers will never learn, no matter how many times you show them the right way to play.