There was another (not incredibly successful) terror attack in London:
We smelled burning wires, and then suddenly, everyone started to panic and started running from one carriage to the next carriage. Everyone was panicking, making their way to the next carriage, screaming, leaving their shoes -- one lady left both of her shoes. [nyt]
I know that the underground is sometimes like a Calcutta sweat lodge, but this just goes to show you why you should not take off your shoes on public transit.