I seem to recall MtGox arranging it so that if you sent bitcoins from your MtGox account to an address associated with another MtGox account they didn't bother making the bitcoin transaction and just credited the account. Does anyone know if this still their policy?
Yup, by default if the recipient address is for another Mt. Gox account, the transaction is internal and never hits the blockchain.
You can mark the checkbox "Open Transaction" for it to always use a blockchain transaction regardless of whether or not the recipient is on Mt. Gox.
- http://en.bitcoin.it/wiki/MtGox#BTC_2
