A big word of caution to holding fiat or large ammount of crypto on ANY online service...
Time and time again there have been hacks or companies running away with money. Leave only what you are not afraid to lose.
Don't make the mtGox mistake. I can also name a couple of other sites where people have lost loads of money, and they all looked safe before money was suddenly gone.
Completely agree but I think it gives people options, another string to bow blah blah.
The exchanges that do it are relatively trustworthy like a BTCe, like a BTER. And I wouldn't see it as a long term thing.
Imagine the next time BTC starts to bomb for some news generated reason then I think many would want to run temporarily to this option for a short time. Or if Bitcoin went parabolic and you wanted to lock away some gains in USD until the inevitable crash. It's definetly useful and definitely not utilised by many people in altcoins.
Once decentralised asset exchanges get more developed like NXT or Qora I guess we can use them for the same function.