It's possible that there were accounts without bitcoin balances.
Although, I still don't trust anything Gox says.
Right. I just realized that. Reference my edited post above...
But... then that would mean that 900,000 of the customers either 1) never deposited any BTC or 2) were smart enough to get it all out before the final goxxing. I wasn't that smart, and I'd find it hard to believe that 90% of users who ever had a balance actually got it out. On the other hand, I wouldn't be surprised that Gox would claim any registered account as a customer, even if it never had any deposit/trade activity.