I had a BTC deposit to my Mt. Gox account from mining and they took it, it shows so in the block chain, and paid it to two other addresses.
Every hosted EWallet service does this.
That isn't YOUR bitcoin address, that is Mt. Gox's bitcoin address. They simply will credit your account for any payments sent to it. Payments from that address go to withdrawal by other accounts or in consolidation transaction that occasionally happens. That's just how EWallet services work.
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http://en.bitcoin.it/wiki/EWallet#Things_to_be_aware_of