I guess many of these BTC have their private keys lost. Nobody ever knows the percentage of actually destroyed bitcoins due to negligence. It's not only the sum that was invested in it's peak, there was certainly some investing/divesting cycles going on so the total sum turned around by the investors is probably > 10.000 BTC. Few percents of BTC being carelessly handled is to be expected.
At the peak we reached something like 65k BTC in the bankroll. Maybe you missed a zero in your guess.
And as Dabs states, this isn't a question of lost private keys (although if I were to do this all again, it would be - multisig is the way forward I think).
Another gambling game ! That's just what we needed , very innovative 
It was, back when it launched. Nowadays it's kind of old hat.