If there are big arbitrage opportunities that is A BIG RED FLAG - why?  because either 1.  you cant import coins, or 2.  you cant withdraw coins.  If the wallets are empty, then cryptsy employees or owners can simply put bids up to entice people to deposit btc (thinking they can take advantage of price difference).  They then make the trade, but cannot withdraw.  From experience, DO NOT TRY IT.  you will get shafted.  Again, not accusing or spreading FUD on cryptsy, this is general advice for any exchange.