A short FP article by Dr. Jeffrey Simon, I assume prompted by the Boston bombing and this passage caught my attention - citing their creativity:
What makes lone wolves so dangerous is their ability to think outside the box. Since they operate by themselves, there is no group pressure or decision-making process that might stifle creativity. Lone wolves are free to act upon any scenario they can dream up. This freedom has resulted in some of the most imaginative terrorist attacks in history. For example, lone wolves were responsible for the first vehicle bombing (1920), major midair plane bombing (1955), hijacking (1961), and product tampering (1982), as well as the anthrax letter attacks in the United States (2001).
Link:http://www.foreignpolicy.com/article..._one?page=full and the author's website:http://www.futureterrorism.com/