OT: you seem confused, inthecards.
Let me post the top part of Ameritrade's e-mail again.
Both you and TD AMERITRADE take on risk whenever a security is traded. While you may be willing to accept any risk associated with this security, there are certain business risks TD AMERITRADE chooses not to accept.
Ameritrade has the buy restriction to protect Ameritrade.
Although it's a moot point, why would Ameritrade care if their customers lost money? If they all lost money, they wouldn't be able to trade and Ameritrade would go out of business.
You say the reason they put on this restriciton, IYO, is "because of the shorting issue". I notice you left out the word "alleged". I will remind you that Ameritrade is in the business of executing trades for their clients, they do not trade stocks for themselves. If you read the fine print in Ameritrade's Customer Agreement, it says:
"Ameritrade does not trade on its own account or make a market in any security. Client trades are executed on independent exchanges, through independent market makers or through ECNs."
I'm sure Ameritrade realizes they are losing commissions here and could possibly lose customers. They must have a pretty good reason for not letting people trade the stock since commissions are their life blood.