once you send the transaction to visa and it is accepted, this information should be PURGED. Period.
Not true. Lots of businesses hang on to your card number, especially if you will do repeat business with them, such as Amazon.
Network solutions is my registrar. They do not keep your CC by default, they ask your permission and there is a very good reason for them to do this. This is why:
My business has a few dozen domain names: our trademarks and a couple of names that are similar (typos that we don't want squatters to snatch up;
Alternatively, we can just allow Network Solutions to keep our CC number and re-register the domain automatically. It is easy and cheap. Of course, this kind of solution requires that Network Solutions not hire a retarded monkey to code its ERM...