Strangely enough, I've never been asked to take off my shoes, even when my wife, traveling with me, has! Though, yesterday (at ~6.15 am), the security agent at BCN, completely agitated, called a policeman when I complained that I had to take off my belt after having gone through the body scanner once without a positive signal and repeat the procedure. The policeman just shrugged and didn't even bother to check my passport, so all was fine after all, but I can tell you that with your flight leaving in 20 min. the idea of having to deal with the police, etc. feels worse than having a hole in your sock.