All smart webmasters use some form of cascading billing. The above comment is correct and the larger billing companies use fancy billing fraud prevention. In my opion its all a bunch of bullshit to protect there own asses. Many providers will decline perfectly valid cards. One of the newest techniques they are using is geographical traces. This means if the credit card billing address is in Florida and the customer is currently on vacation in Massachusetts and tries to signup, it will decline.

Its smart to have 2-3 billing providers for your site, and run them in a different order. Everyone who didn't do this has learned a HARD lesson after ibill disappeared with all there clients. Balance your billing or pay the price in the end!