While not everyone working for these companies is above suspicion, they have strong policy controls in place to prevent unauthorized snooping. They have a vested interest in insuring no such eavesdropping is taking place, since they stand to lose a great deal of business if such eavesdropping is discovered. Further, since many of these companies deal with credit card payments, they fully understand the need for security. Of course, despite this, credit card number theft does occur. But, even when it does, the consumer is strongly protected.
Laws limit the amount of liability a customer has for fradulent charges.
Many credit cards now have a 'early warning system' if your card is used from an unusual location or in an unusual way. However, I also realize many good companies simply don't have the money required to obtain, build, and maintain a secure server.