Bitshares is not a centralized exchange, so it cannot be hacked. E.g. even if the server of Bitshares gets hacked, they can only bring the website down, they do not have access to your coins because you own your coins via your password and key. This is how Bitshares is different from Centralized exchanges, your coins are not saved on the server.
RE: Finally I'm on Bitshares & Here is My opinion about BitShares [Some Basic Ideas Are Given]