Lynnafred took this pic of a lobster in the tank at Waldbaum's in West Hartford. He was right in the middle of chowing down on his cellmate, whose partially-eaten corpse may be seen, belly-up, in the lower left corner of the picture. Notice that the lobby has enough strength in his left "crusher" claw to open up a little despite the rubber band supposedly holding it shut. That's just enough to be able to get a grip on an opponent who's too weak to resist.
You may not know it, but that is the real reason why lobsters are marketed with their claws held shut by rubber bands. Fishermen already know how to handle lobsters without getting pinched. Wholesalers and retailers really don't care all that much if some mook poking the bugs gets a claw-induced blood blister. No, they clamp the claws because in the stress of the overcrowded holding tanks, the unfed and agitated lobsters turn on one another and would tear each other apart before they can be sold.