Sorry, but I have to agree that your friend did 
not make a very smart trade from the start.

Someone please correct me if I am wrong, but I
believe only part of DBZ has been officially
subbed, thus if your friend was supposed to
receive that many episodes, he should have known
that he was going to get fansubs and not anything
better.

Also, he should have asked what program they 
would be viewed on his computer.  Any time you
hear the world "realplayer", run like hell...

And I think Aaron knows very well that trading
back would not be mail fraud.  And I doubt
Funimation actually contacted him personally.
More than likely, he had that as a prepared 
excuse because he knew he was senting crud and
knew your friend would want to trade back.

Chances are there is really nothing he can do but
take it as a hard lesson learned (who hasn't had
one?).  In the future he should probably only
trade with people he knows, people who can get 
someone he knows to vouch for them, or trades
where he receives before he sends.

You can try to save every email and eveything 
else to document your case, and then as someone
suggested, contact the police department in his
area, but I have no idea if that would help.

You could always say you have all the emails and
paperwork and if he does not comply, your aunt
(uncle, father, brother, etc) is a lawyer and you
will take him to small claims court.  Or, my 
personal recommendation, call Judge Mills Lane 
and see if he'll take your case on his show: 
Let's Get It On!!

Sorry for his trouble and good luck...

ksg