I recently went through this shoes fiasco in LAX, everyone's shoes setting off the machine...huge queues...shoes through the x-ray machine etc...where as at LHR a wave of the detector wand over the soles was considered quite sufficient...
My shoes are middle of the range all leather soled and resoled with a token 3 small tacks in the toe end and metal lace eyelets...setting off the machine no doubt...
The security 'moron' asked me why my soles had tacks in them...he seemed surprised at the explanation of being resoled...clearly because a peasant like him has not come across quality shoes!
PS. he was clearly an immigrant with an unintelligible accent and looks that would certainly raise concern as to his origins and security risk...had he not been an airport employee!!