This is not a major issue, but I am curious about TSA practices. I have made 5 trips this year from SFO. When going through security in the UA terminal, on 3 occasions I had to remove my sneakers. On the 2 other occasions I did not. I always wear the same pair when I travel (for comfort). There were no heightened security alerts any of the times I flew. Saturday I asked the TSA rep why I did not have to take them off this time... her response "only shoes with metal need screening". Does anyone know what the true policy is?