this the explanation thread about leverage with some example, which i got it from some Indonesian forex forum.
this like you want to trade some car with $10 k on some car dealer. Then you buy the car with just $100, the car still on the dealer, but you have the right to trade it (open trade), when the car price up to $10.500, you get = $500 profits - fee (spreads on forex brokers). So if that's happen and the fee from the dealer (to pay their service) is $20 (for the car type which you trade it) you get $500 - $20 (fee/spreads (on forex brokers) =$420. When the price of car is down going to $9.950, then you still hold it (trade position still open), that's means you are on floating loss position. When the price down and touch $9.900 in market, then you loss your capital = $100, it's called margin call. So the brokers would loss nothing for this leverage facility, and traders no need worry for this leverage facility, just use right leverage option according with your money management of trading.
hope this explanation can help others, if still don't undertand, please post there.