Well, this is why you should keep your own bitcoin wallet. Bitcoin theft isn't a problem with bitcoin itself. It's a problem with where you're keeping your bitcoins.
No, BTC theft is indeed a problem with BTC itself. Evolution operated a BTC escrow service between its buyers and sellers. Unless the buyer and seller trust each other implicitly, escrow is essential for large remote transactions to ensure that no one gets ripped off, because (as we all know) BTC transactions are irreversible.
What Evolution did was empty out its escrow accounts and run off with the BTC from all the pending transactions. There is now essentially zero likelihood of them being punished, or the BTC being recovered.
And there you have the problem with BTC in a nutshell. Whether you use an exchange to transfer BTC to fiat, or use an escrow service to hold it pending a transaction, who do you trust to do the job? Particularly in an unregulated, pseudo-anonymous economic model where theft and graft go unpunished on a regular basis?
BTC has jumped the shark and is now moving into the long-term "let's keep fleecing the newbies" phase, just as you see with gold and silver "investment" companies. As long as there are suckers willing to exchange good money for BTC, there will be a very long line of criminals ready and willing to take it from them.