How hard is it to transfer money between Bitcoin exchanges? Say I had a 100$ in a Mt.Gox account and wanted to send it to my TradeHill account, how hard is it to perform a transaction like that without going through a separate bank account? I'm mostly asking in a context of automated trading bots, buying and selling Bitcoins at different exchanges.
That's exactly the service https://www.bitinstant.com/ provide, it should be fairly simple and I think they and mtgox have the API necessary to do this by a bot.