What is the purpose, or reasoning, behind the $100 floor on personal casualty losses? After reducing the loss by the floor, the 10% of AGI limitation is then applied, which almost always will result in a greater reduction to the loss before arriving at the itemized deduction amount. The $100 floor seems very, very immaterial. Is there something that I'm not understanding regarding the relevance of the $100 floor?

agreed.I guess no proper reasoning or logicality. it is just what/because the tax law says.