Most of the report focuses on bleeding edge spying techniques like using the mobile phone as a surveillance device, tracking individuals by their GPS signals, and how voice changers can be used by those looking to avoid being tracked. Once they finally got into how Twitter can be used, though, it looks like they really thought outside of the box; but as I read through the report, there's not much being described here that can't be done with a myriad of other tools.
For instance, they describe a scenario where someone who is friended with a government employee privvy to state secrets can be social engineered into divulging classified information to someone they think is their friend, but is actually a friend with a terrorist-hacked Twitter account. In another scenario, they describe the use of a Twitter-connected mobile phone as a remote detonator for an improvised explosive device. It might work to help obfuscate the person who sent the detonation code a little, but no more so than a hundred of other tools available on the Internet that can allow free sending of SMS messages.
As you might well imagine, Twitter isn't a great tool for planning cover operations. Everything is out in the open, and depending on your circle of friends, you're likely subject to enough ridicule and pejorative as to offset any sort of positive spin on extremist propaganda you might be trying to spread to the masses.
Jim Harper over at Technology Liberation Front put it best today:
Securing against terrorism is hard because terrorists don’t wear uniforms or occupy territory. Their tools are our tools: sneakers, sandwiches, credit cards, cars, steak knives, box cutters, cameras, cell phones, driver’s licenses, Web sites, Napster, Friendster, Facebook, spinach. The list goes on and on and on.