My best recommendation to you is to forward your complaint as well as any information that you have on the guys/ guy that scammed you to the FBI. This will ensure that if this guy ends up being a truly bad figure who is taking money from Americans in order to finance terrorism or to damage our business efforts in the future, the FBI will have EVERYTHING that you knew about this guy ahead of time and YOU yourself would have submitted it.
I don't know how well the grassroots system works against online fraud: I would assume not very well.
If you are interested in filing a complaint though, go FBI all the way: they are the ones that will handle this garbage when it all shakes out. On the other hand, if your computer has been subjected to viruses, illegal cookie activity or otherwise, you may do better joining the Marines and "whacking off a few" on the count of too many people attempting to gain access to too many arenas of new age tech.
I'd guess you'll opt with the FBI.
Otherwise,
Semper Fi,
Enjoy,
Jason Mueller
Mueller Computing Concepts
Http://www.muellercomputingconcepts.com