We've always wondered whether BART was as likely a terror target as the New York City subway system, and always suspected that no, it isn't. But you may have noticed some stepped up security patrols on trains, complete with bomb sniffing dogs, the likes of which we haven't seen since around October/November 2001.

As a result of recent arrests in New York City of Al Qaeda suspect Najibullah Zazi, as well as his father and his imam, security at mass transit agencies has been stepped up nationwide under fears that he was only one member of a multiple-cell unit. The actual bombs or explosive materials have not been found, but Zazi had a complete bomb-making recipe on his computer, as well as maps of subway tunnels, Grand Central Station and several stadiums. Zazi, who is 24 years old and Afghan-born, admitted to receiving explosives training at an Al Qaeda camp in Pakistan, where he had traveled twice in the past year.

There is of course no reason to believe San Francisco was part of the plot, but yes, we might as well become paranoid again anyway.