Poloniex just proved us they don't run a fractional reserve for BitShares at least. What if the exchange you used could do this for whatever coins/assets you hold? Wouldn't you feel more safe and have more trust on their service?
Other exchanges can do the same. There are currently a few projects and exchanges working with OpenLedger to bring a better service to their costumers, this includes speed, safety, more market depth and overall performance.
Wouldn't you like if exchanges were more transparent and you could own the private keys to your funds? More info here if you're interested:
http://www.forbes.com/sites/rogeraitken/2015/10/10/openledgers-crypto-financial-platform-officially-launching-as-central-bank-interest-revealed/
https://openledger.info/
Now, will other exchanges follow?
Many exchanges claim to be the most transparent, but unfortunately, there’s no single one-fits-all to this. Ideally, the crypto-asset must need to have an integration plan with several exchanges with adequate information about its commercial purposes, in this way it will be possible for users to easily transact with it without compromising their security. After this, market prices will be the determining factor on the crypto-asset price without interference or manipulation.