Go for it 1:100 is a minimum so you can make 10000% when BTC makes 100%. (Or rather lose everything in few minutes).
There is some margin trading on btc-e.com, it was sth like 2 or 3:1.... Wonder how those people trading with that leverage there felt while fat finger flash crash happened.
Stupid idea really as you can lose more than you actually have on your account. Actually every person who was buying on btc-e with any leverage had to be stopped out as market fell 85% losing everything maybe owning something to btc-e.com as a market maker and other side of the trade.
I do not know how many people trade there on margin but I do realize now that the crash could have been caused directly by btc-e as it will be profitable as hell closing all those margin longs..