Depending on all of the circumstances, this could result in one or more of the following:
1. a non-business bad debt deduction
2. a business bad debt deduction
3. an increase in stock basis leading to a loss from the sale/disposion of the stock.
Number 1 results in a short term capital loss, number 2 results in an ordinary loss, and number 3 results in a capital loss that is either long term or short term depending on when the stock was acquired vs when it became worthless.