Questions regarding BB/100

[nickabourisk]

I was just wondering about a couple of things. For one, I've heard that in limit, you should make ~2BB/100. Where does this number come from? Is it determined experimentally by winning players or is there a way to derive this? Secondly, at the smaller limits such as $0.25/$0.50, this should probably be much higher for a winning player, right? Any clarification would be great. Thanks.