We always triple check with followup emails, request for copys of a drivers licence's etc if the order meets one of these criteria:
1. Comes from a country outside US
2. Someone orders a expensive plan theyve never contacted a sales person about.
3. The credit card information does not match the customers information.
4. The email address is that of a free public email service.
If it meets one of these criteria, your best bet is to followup with a email/or phone call if in US (even better), and getting some more info, and if it still seems fishy even in the slightest bit, make them fax in 2 forms of ID.
Weve used this procedure for 7 years and have never had one fraudulant customer, weve caught prob. over 100 people before they became customers.