Do you retarded litecoin supporters think adding feathercoin to mtgox would help eliminate arb opportunities too?  How about ixcoin?  Adding litecoin would only help arbitrage if the litecoin market cap was LARGER THAN BITCOIN.  Adding a tiny market to an exchange does nothing to smooth rates out because so little money can be funneled through the link before it creates another differential and arbitrage opportunity there.  Adding USD as an option, however, MASSIVELY helps smooth out arbitrage opportunites because USD market cap is way bigger than bitcoin so nothing happens to the USD market when you send 100k USD from japan to bitstamp for an arb.  The arb opportunities only exist because of the fees and wait time associated with sending USD wires.