I have personally received "minor threats" but nothing as extreme as your case. We've had bad people use horrible language where techs informed me he needs to go...
The IP matching is vital in proving services rendered to clients who claim they never received services and matching things up such as emails. (Send emails to the same email used to place the order!)
Also, every order needs a confirmation that client agreed to TOS, AUP and SLA.
Confirmed PayPal accounts also help significantly in our experience with cc fraud.