Surely this idea needs rethinking/recasting. http://blog.wired.com/defense/2009/01/nypd-eyes-disru.html
I would imagine attack planners would have backup plans in case they lost communication in any scenario. On the other hand, ordinary citizens wouldn't - no warnings to family members, no reports to authorities. Ordinary people enabled by communcation technology brought that 9/11 hijacked plane done in Pennsylvania - avoiding greater catastrophe in Washington.