I would like to see the stats on how many people actually unlock their phone with the intention of switching to another carrier.
With iPhone, all the carriers have it anyway. iPhone owners ususally just jailbreak to modify the way the OS works.
Android users unlock their phones in order to be able to put custom ROMs on.
I've hung around a few android forums in my day and have never seen a post that said "I can't wait to buy a Droid Razr, unlock it and then run that bad boy on AT&T!"