I think this is the first case of a shoe bomber since Richard Reid.
http://www.timesonline.co.uk/article...229163,00.html

He made it through two stages of security, up towards the front of the mosque, when some people spotted that he still had his shoes on (they are supposed to be removed). It seems he had explosives and ball bearings in his shoes, and the detonator was not a cigarette lighter and fuse.

X-rays would have picked up the ball bearings, but if they had an x-ray system the bomb would just have been constructed differently. However, with a shoe carnival, it would have been spotted earlier that he was putting his shoes back on. That isn't analogous to an airport situation.