While doing research for something else, I came across the following page on CompTIA's web site.
Unauthorized Third-Party Training Materials and Offers Policy
It lists specifically which sites CompTIA considers unauthorized. I hear people sometimes ask what is considered unauthorized training materials and this link makes it pretty clear what CompTIA considers unauthorized.
The page also talks about unauthorized vouchers. I haven't heard about anyone paying for a voucher that was found to be fraudulent or already used, but for CompTIA to put it on the website makes me wonder if this is actually occurring.
Darril Gibson
Author: CompTIA Security+: Get Certified Get Ahead
ISBN-10: 1439236364
Security+ Blog
Security Plus: Get Certified Get Ahead