Boston is a reminder that: Open source warfare doesn't ever go away.
It can be revived with a terrible suddenness, as we saw at the Boston Marathon.
The grievances and motivations for attacks never die. They can always find a corner of the Web to fester and grow, in groups too tiny to ever control.
The information needed to conduct attacks will always be available, and with each round of incidents, the information improves through testing.
Due to excessive industrial urbanization, the targets both in terms of people and infrastructure are thick on the ground.
Any single attack has the potential to ignite a series of additional attacks by other groups with similar, but different, motives.
Due to technological and behavioral factors, the quality of the attacks can better very quickly once a a conflict ignites. Weeks can yield significant progress instead of years.