The biggest lesson from Gox saga is that you can't trust any exchange in their current forms. If Gox can go this wrong( with Mark a high profile public figure, Bitcoin Foundation Memeber, registered in developed market), you basicly can't trust any other (btc-e, bitstamp, coinbase);  Just keep the minimum you need for trading and store the rest offline.

All bitcoiners, withdraw all your coins from the exchanges/online wallet and keep in your own wallets (except those who need to maintain certain amount for day trading or expense), keeping coins in exchanges will only lend them more incentives to gox all your coins to the air.

All BTC exchanges/online wallet, structurally are operating a fractional reserve scheme, but without a proper protection that you could expect from a bank (which is also fractional reserve model).  

Until the industry is ready to build a distributed or reserve verifiable exchange, don't keep more coins than necessary in an exchange.

The more coins you keep in an exchange, the more likely you are aiding the emerge of the next Gox and feeding evils in the ecosystem; For bitcoin's sake, keep all your coins in your own offline wallet.