Wild guess, but probably smartphones. Never before has something been so easy to take (it's just in your hand and not tied to anything, unlike a purse), worth so much money, is so easy to conceal, and is so universally demanded and easy to fence.

I think the article had a good hypothesis: the duality of gentrification (there is no way Oakland can't gentrify given the price of living in the City) and that the other half of people in Oakland were hit unreasonably hard by the recession. A little microcosm of growing economic inequality.

As a startup venture, this rate of increase does not pass a significant investment criterion -- for me, at least.