It seems Giusti had rather overstated his clandestine skills as a wannabe domestic terrorist. Giusti allegedly used the Internet phone service Magic Jack to make his threatening calls. And in one call to Pelosi's office taunted "and the number I'm calling from is untraceable so if you're trying to trace it have fun."
Needless to say, though, it seems that the security mountain in front of Magic Jack was no match for the tech folks at the FBI. As the first commenter on the post snarked: "Another idiot is rudely introduced to the difference between what your casual user can get from caller ID and what the FBI can do when it wants."