Margin trading cryptocurrencies

[Ploo]

Are there any places to do this?

And more importantly - is this viable? Could margin trading be offered in the world of cryptocurrencies? I don't mean established pairs like BTC/LTC but small altcoins.

Naturally this could be difficult due to the immaturity of altcoins. Theres little liquidity, little volume and I assume other unfavourable factors. Although, suppose its your own exchange (and you're not a meta exchange like Bitfinex once were) and you can post a stop loss at exactly the right level and guarantee it executes - as long as you can satisfy every margin call then everything is dandy - surely?

Originally BitFinex would act as a meta-exchange and place orders at bitstamp and other exchanges. This explains the necessity of them having creditors on the site from which to borrow money.
Today they trade on their own exchange only meaning that they don't need to borrow money to open positions. I suppose it makes sense to actually borrow money from someone interested in lending it - but is it necessary?

It is my understanding that the practice of an exchange opening positions without the asset backing is a naked call. How common are naked calls in the real world? Would it be a good idea for a cryptocurrency exchange to offer uncovered positions? What are the possible implications of doing it this way?

Can anyone offer any thoughts and ideas?