Today, Bitfinex was hacked. Almost 120 thousand bitcoins were stolen, and the exchange has been taken offline while they access the damage. If you have not already done so, you may want to remove any Bitcoins from any of the exchanges into a cold wallet, that are not being used for active exchanging. Here are some good instructions for generating a paper wallet. http://www.coindesk.com/information/paper-wallet-tutorial/
You may want to experiment and only transfer a small amount of Bitcoin, first, and make sure you are familiar with how to recover your bitcoins, before generating a new wallet. Make sure to keep your paper wallet in a safe place and you may want to also record your public and private keys in a text file and store on a USB drive.
It cannot be stressed enough to never store your bitcoins on any online exchange. Throughout the history of Bitcoin, many exchanges have gone by the wayside. Also note, that there is suspicion that many of these hacks are just a cover story for some misdealings with the exchange itself. Examples that come to mind are MtGox and Crypsty. Have some peace of mind and store your unused bitcoins in cold storage.