Steals happen more often in tournament situations due to the escalating ante/blind structure making the starting pot quite valuable.
Of course, skilled players will recognize repeated steal plays and frequently reraise for defense.
An aggressive player, especially one with a large stack of chips, might reraise, also known as re-steal, someone he knows might be trying to steal.
The objective here is twofold: the re-raiser hopes to pick up both the blinds and antes and the original raiser's chips when the raiser folds, and he also hopes to keep that player from constantly raising before she or he can act because that cuts down on the reraiser's own stealing opportunities.
The original raiser will often only continue with a truly premium holding as several other players have shown signs of strength, and he may well be playing out of position.