Bitstamp have been running a fractional reserve for years. This hack story is an obvious lie, copied from Karpeles. During the next weeks we'll learn about Stamp's insolvency. Then they'll declare bankruptcy, and all your precious coins and fiat will be lost.
And if the story was true: What's stopping the thieves from hacking them again, stealing even more?
I would love to see where you get that information from. Bitstamp has been relatively open about their reserves for exactly this reason, consumer confidence.
And about the hacking again theory; if you own a boat that has a hole in it, you don't let it sink to the bottom, you plug the hole and move on. Finding and fixing the leak is exactly why they have suspended their systems.