I've seen tablets used as a household appliance akin to a TV or family computer. I'm not saying this would never be useful on phones, just that it's more obviously useful on tablets and TechCrunch seems to ignore this in favor of a more scandalous conclusion.

Just out of curiosity, how often do you let someone else use your phone? Not check out your phone but actually use it to the point they'd require a guest mode? Guest mode on a phone is like flying lunches in via Concorde from Paris.