It's tough to concentrate on work while thinking about the bombings in London. Like so many others who were within spitting distance of the terrorist attacks of September 11, 2001, it does not take much to transport me back to that day. And as I sit in my office now, floating 14 stories in the air overlooking Boston Harbor - at Boston's own diminutive World Trade Center - I can't help but cast frequent nervous glances at the airport and the tankers and barges that meander past in the inner harbor.
I am amazed that coordinated subway attacks like today's in London or the attacks in Madrid last year do not happen more often. Perhaps their relative scarcity is an indication that making and transporting explosives is not quite as easy as it seems. Or maybe it means that people with the desperate and warped perspective required to undertake such an attack are not as legion as it seems. Either way, it's not much comfort today to the people of London that terrorist attacks are rarer than you might think.