There is another way to view leveraged investing. It allows an investor to keep most of his invested funds under his own control. Let's say he wants to invest 10 BTC but feels the risk of hackers or the owners runningoff with the money is o high, then he can "borrow" 9BTC and deposit only one. It's not really leverage in this case. Just risk management.
Hmm, that's a good point and interesting way to look at it. I much rather have 1 btc at the site than 10!