If everyone folds around to the blinds in holdem, it's common for the two players in the blinds to "chop," meaning they take their blind bets back and move on to the next hand. In Los Angeles, $1 is taken for the house from the person in the small-blind. In Las Vegas, the house takes nothing. On the other hand, if there is a flop, usually there is a lot more taken (eg $5 more is taken in 20-40 limit holdem at the Bike if there are at least 7 players). There is an unwritten rule (it is rather strongly enforced socially at the poker tables) that you should either always or never agree to chop when given the opportunity. This means that you shouldn't be looking at your cards, seeing AA, and deciding not to chop if you have established yourself as someone who does not chop. I'd say that at least 90% of players agree to chop, but if either player refuses, then the two players play the hand out heads-up.
I recently stopped agreeing to chop. Although I don't like having to pay the extra $5 to the house for what is often a small pot, I think it's worth it because I have a big edge against most players, and lots of players play even more poorly heads-up. One issue for me is that there is social pressure to chop. Some people take offense if I refuse to chop, and in fact, this was the main reason I ever agreed to chopp in the first place. It didn't seem worth making enemies. Since I had been chopping with people for the past several months, I was in particular danger of angering people by not chopping with them all of a sudden. On the advice of another prop player (Johnny), I made myself a little sign on a sticky-note saying "no chop." After a day or so it was defaced with "Please Raise Me!" Now I use a slightly larger sign that a player made for me. It's pink and says "please Raise me! NO CHOP" It's ridiculous enough that it seems to defuse any animosity towards me.