As far as I'm concerned, MyBitcoin never had any stolen BTC. The operator had BTC that a bunch of people gave him thinking that he would give them back. Poor judgement and/or laziness and/or lack of understanding of Bitcoin/money/human nature.
'jav' has got some coins I gave him using his instawallet.org service. If he walks off with them, sad day for me, but I'm certainly not going to go crying to the police or bitcointalk or anyone else. Nor am I going to hunt him down. I've put a significant amount of thought into how to protect various of my assets, and those who cannot stand the heat should stay out of the Bitcoin kitchen until the system develops more in my opinion.
Unfortunately we are in a phase now where it is becoming less practical for people to protect themselves in the 'real' way (by running a bitcoin client) due to bloat, but as far as I am aware there are not any on-line wallet services which allow the customer to control their private keys.
Bullcrap, of course. If mybitcoin had billed itself as a site that might walk away with your bitcoins, you'd have a point (and they would've had no customers).
By your faulty logic, if my bank decides one day to not return me my money, I'd have no recourse. It is ONE way in which a society could be run, but it wouldn't be a very good place to live.