It's getting more common but not every card issuer has it yet. Citibank has a downloadable program that generates extra account numbers for all their credit cards. You can generate as many as you want, and specify if you want them useable only once, or if you want to specify their charge limits and expiration periods and use them multiple times. Citibank calls them Virtual Account Numbers ... and they track each one's charges separately, and you can cancel them online:

https://www.citibank.com/us/cards/index.htm