But what if someone picks up your phone at a party while you're just a few feet away, and they decide to be a dick? It would take them just a minute to erase all your data.
If they are worried about bad guys deleting all their data, they should stop leaving their phone around at parties. Getting their phone stolen is an even worse outcome, because the data is effectively deleted and the hardware is gone. And it's strictly easier than stealing the phone, deleting the data, and returning the phone, which is what the ggp comment was suggesting we worry about.
