Thoughts on Boston.
With some exceptions, and perhaps because the number of deaths so far is 3, which is still 3 too many but seems close to miraculous given the number of people in the area and the way the bombs were constructed, the response so far has been measured. The decision not to describe the attack as terrorism immediately was undoubtedly the right one, and the reluctance to do so even today also feels right. Fundamentally, regardless of who or whom planted the bombs, the act remains a criminal rather than a political one. As for who could have carried it out, it realistically could have been anyone: while it doesn't seem to fit the usual jihadi modus operandi of suicide or car bombings, the Madrid attacks were carried out using planted bombs, and it should be remembered that the recent push from ideologues has been for individuals to launch attacks on their own. Relatively unsophisticated devices such as those used yesterday could well have been constructed by someone with no formal training relying on information gathered from the internet.
Similarly, the perpetrators could just as easily be far-right extremists, the attack coming on both Patriots' Day and Tax Day, close to the anniversaries of both the end of the Waco siege and the Oklahoma City bombing. Indeed, Timothy McVeigh carried out his attack on the old date of Patriots' Day. It could also be the work of someone with a similar ideology to Eric Rudolph, most infamous for the bombing at the 1996 Atlanta Olympics. Other suspects, although less likely, could be a far left/anarchist groupscule, or a lone agitator, the most notorious American example being the Unabomber. Wild claims on Twitter that it could be connected to the on-going tension with North Korea seem extraordinarily wide of the mark, not least when the North has never carried out any attacks against a country other than the South.
Understandable as it for there to be concern about the London marathon due to the proximity of the events, there isn't the slightest evidence that yesterday's bombing was anything other than an isolated incident. Not only have there never previously been terrorist attacks carried out by the same perpetrators in different Western countries separated by such distance within such a short space of time, security is always going to be inevitably ratcheted up, thereby discouraging any group when the chances of being discovered are increased. Whoever planned the attack, despite having so far failed to claim responsibility, knew full well that cameras would be focused on the finish line, guaranteeing that the explosion and the moments after the blast would be recorded for maximum effect. If they intend to repeat their success, then it's unlikely that anywhere less well covered will be chosen, thereby increasing the chances they will quickly be discovered. Indeed, it would perhaps be more surprising if the person who planted the bombs hasn't been captured on film at some point, especially as the area had previously been swept for devices twice in the past 24 hours, necessitating the devices being left within hours of the race beginning.
This all said, the best way to respond such attacks has always been with empathy, sympathy and stoicism. Life goes on, and always will do, which makes such references to "9/11 spirit" so thoroughly lacking in rigour, as were the ones after 7/7 which remarked on how Londoners carried on using the Tube as though nothing had happened. Surprisingly, people have to carry on making a living, which is all the more reason to help those who have been directly affected rather than comment on how everyone manages to keep on going as though it were something remarkable. It also ought to bring into focus how some live with the real threat of such violence on a daily basis, as others have said. That we are either indirectly or even directly funding some of those carrying out acts we would describe as terrorism were they to hit our own cities might shock those who have been so outraged by a terrible but also inevitable (such is the history of terrorism) event.