If they are going to charge with money laundering they have to talk about the flow of fiat currencies specifically $US
If they are going to map out what bitcoins from MtGox went into which accounts, and where the fiat or BTC from those accounts were forwarded, it's going to take a loooong time to dig through logs. I'm guessing they do not want to enable the site, in case some of those funds are still in BTC-e accounts (as they would be quickly withdrawn as soon as the site is up again). Perhaps it can be enabled with withdrawals disabled, at least for unverified accounts.
Still feels like it _should_ be possible to take the site online again while still cooperating with the FBI, I hope they understand that funds from thousands of innocent users are being frozen and can figure out a solution.