This is really a lending business, you lend me your money, which I pass on people who want to trade with leverage (hence the "swap" and the remunerated deposits). When I can't hedge positions, you can't pass an order, as simple as that. But it's my understanding that every financial institution uses customers deposits to trade. What they also do is cover them with an insurance. Which currently we don't do.
There is another thing: in many conventional lending businesses, there is a limitation on what you can withdraw in a given time span.
To the contrary, here in Bitfinex the part of the deposited sum which is
not used in positions may be seen to form a pool, together with the existing reserves of the platform. Effectively the contents of that pool are what can be used as leverage to open positions. When this pool is exhausted, users get "the starfish". So far so good.
But the problem is: there is a promise for the account holder to be able to withdraw any time (just a short security timespan to confirm the withdrawal, but no limitation on the amount). On the other hand, there is no way to make any users close their positions. Thus, when a user withdraws, he re-calls money which is bound into a position on the market, with unlimited duration. Assuming this situation, the platform is forced to turn into a "bucket shop", even if unclescrooge never wanted to do this: Assumed there are no further reserves, the platform is forced to close some positions
internally to get the money for the withdrawal request, while keeping those positions opened
nominally. So effectively the platform is forced to take a counter position to these internally closed positions, i.e. bet against the user.
Why did I say "bucket shop" here? Simple:
- Contract for Difference => swapping of cash-flows and risks
- "bucket shop" => a betting business users against the house
Incidentally, whenever a position is opened, the premium (on top of the actual market spread) can be immediately accounted to the liquidity pool.
Thus: larger premium => better chances for the platform to become more solid financially.