You can still take a loss for an investment scam entered into for a profit.

The Chief Counsel memo affirms that taxpayers who are victims of scams may claim a theft loss deduction under IRC § 165, but only if their situation meets specific conditions:

• The loss must result from criminal conduct classified as theft under applicable state law;
• The taxpayer must have no reasonable prospect of recovering the stolen funds; and
• The loss must arise from a transaction entered into for profit.