It just came to me that there are unknowns to myself out there in this world that can make me broke. I don't know what these unknowns are. But I can give you an obvious example of such unknown in tax law (to some people, not me) so that you understand what I am talking about and help me to find more such unknowns. A dude traded frequently but had no idea of certain details in the tax law. So he thought that he ended up the year with a total short term gain +0.5M (1M gain and 0.5M loss, all short term). However, since he did not claim trader status and is unable to claim almost any loss due to wash sale that restrict him in some not obvious strange way. Anyway, now IRS wants tax from him. He can do nothing but go file personal bankruptcy. This example may not be realistic. But what I mean here is that there are some unknowns in tax laws, exchange/broker rules, or elsewhere that can broke you and me because we trade and trade too much. Can you give me more examples, please?