>Ok, I may be incorrect and maybe they do get deleted. But then how do >they register them first? Are all of these companies running constant >checks on the domains to see if they're available yet?
Well most services check during the batch drop. If you drop at a random time ... and then notify the other party so they can register the domain the instant it drops it still could be technically "released" and re-registered. I don't know that this is happening here or but it is certainly a possibility. One of the SnapNames State of the Domain report discussed how domain hijackers were moving stolen domains to different registrars using the delete command.
