Conspiracy theories are not necessary in this case. MtGox has had extensive know your customer procedures in place for a while. FinCEN recently issued explicit regulations for Bitcoin and MtGox indicated that they're already "overcompliant" with them. And MtGox is moving from Japan to the US just to be sure. There's no evidence that MtGox is sending every transaction to the US government, but it sure looks like they would voluntarily do so if asked; no hacking needed.