By your logic, ASICMINER is worth around 10% of total BTC.
If ASICMINER or anyone else gets over 50% of the network hashpower, then the BTC price will crash even if the controlling party doesn't do anything nefarious.
well if the stock is trading at 1btc 400,000 shares is 400,000 btc which is ~4% of total btc.
Not all 400,000 shares are/will float, and it's trading at 0.85 on BitFunder.