haven't done it myself, but this is what I've been told.
A lot of it has to do with how you stack them. the supports are on the very edges of the bricks, making them bend and break more easily. When someone breaks a stack, most of the time they have little spacers in between so its not just brick on brick. stacking two bricks together is a lot harder to break than the same two bricks with spacers. People have also said that if you think about hitting the brick, you hurt your hand, but if you think about hitting past the brick, the brick breaks. like I said, I've never done it, so I don't know for sure. this is just what I've been told.