It has been the hot thing to make kill switches for phones recently. Carriers have been asked by government agencies to do it, states are passing laws to require it, Apple did it, and now Google is implementing it in Android 5.0. Lollipop will come with an opt-in "Factory Reset Protection" option that keeps a thief from being able to wipe your phone, making it a less appealing target in the first place.
If you activate this feature, your Google login will be required to factory reset the phone or tablet. Presumably this will also prevent factory resets through recovery—otherwise it would be pretty useless, wouldn't it? A secure lock screen of some sort will be required for this feature as well.
Assuming people actually use Factory Reset Protection, the incentive for stealing phones and tablets will go down dramatically. If the device can't be unlocked or wiped, it's just a pretty chunk of metal and glass.