Perhaps I should not have used the phrase "essentially worthless." As long as the stock is still listed (on the pink sheets, for instance) and is still traded (or tradeable), you don't have to cover. Think about it: if KKD trades on the pink sheets for .037 per share, which is 0.1% ($380) of the hypothetical investment in my previous post, can the IRS make me or any ones else buy or sell? Ever? Of course not! I can hold out in the "hope" (ha!) that the stock price will recover.
This issue has been hashed out in detail in previous posts by Mungerian and others. Take a look.