Yet, transfer protocols secure data only while it's en route. Once the data is on your server, it's much more difficult to ensure its safety. Consider a Web site hosted on a virtual server with 100 other Web sites. Each one has its disadvantages.
Email is perhaps one of the most basic ways to receive and store credit card numbers.
Many smaller companies have their order forms feed into a script that packages customer data into an email message. The message gets sent to someone in the company who later processes the order manually. If your company uses this method, hopefully your business practices require you to encrypt each message before transit and during storage. If not, consider how many machines your email travels across before it reaches its destination. If someone accesses your email while it's in transit or while it's sitting in plain view on your desktop, you could be in for big trouble, legally and financially.