[Blarg]

I agree. My first thought was that BB had a weaker ace and wanted to throttle the betting by betting less than the pot, and hopefully chase one or both players out.

If he had a really good hand, this sort of stop and go bet wouldn't be necessary. He could let either hero or MP2 bet the hand for him, and build it up, instead of taking a chance of either losing all further money that could be put into the pot by betting out unnecessarily, or at least cutting back any possible betting to a minimum, including a push into him which could be great if he's REALLY got the goods.

An ace on the flop in a three way hand where there was a raise and re-raise will almost certainly draw a bet from either BB or MP2 whether they have an ace or not. Especially if MP2 raises preflop and doesn't get raised back, he knows he either has the best cards, or that if he doesn't pretend he does on an ace flop after two people check to him, they're going to know the jig is up and that he doesn't have an ace. At that point, they may put him on something like a pair of jacks, and know not only that any held ace beats him, but that even a pure bluff is very likely to make him fold if the turn is a blank. So MP2 is almost obligated to bet the flop or face folding on the turn to any bettor.

This bet out from BB just does not strike me as evidence of strength, but as an attempt to shut down the betting so nobody bets or bluffs big on that ace, and to maybe even snatch the pot outright for cheap whether he's already beaten or not. I would often expect BB to turn over a medium ace, as many people are blind happy and would love to call such a small raise if they were already in the blind.