The services are heavily marketed to cardholders, particularly when you call a toll-free number to activate a card or ask a question, or when a customer-service rep calls to answer an inquiry.

WSJ: Getting Going: The Financial Fear Mongers

Same for when you activate a credit card over the phone, or call a 900 number.

FORBES: Get Katz

Another adds an extra level of security with a code needed to activate the card.

FORBES: Credit Cards Reimagined

Now, music fans in Mexico, Ireland, Iceland, Italy, Latvia, Lithuania, and Austria can sign up and activate free streaming at rdio.com, without entering a credit card, then dive right into Rdio's library of over 18 million songs.

ENGADGET: Rdio on iPhone now shows which friends are listening, web streaming hits seven countries