1. The points or miles are not transferable to other programs. You may not transfer "miles" in the program to any airline miles account, and thus you may not combine these miles with real airline miles.
2. The only way to earn "miles" is by spending money on the card. Unlike real airline miles programs, you cannot earn "miles" via telephone offers, financial offers, etc.
3. The points or miles usually expire after a period of time, usually two or three years. So you must be certain that you will spend enough on the card within that time period to get the award you want. This may mean that for a ticket you will have to know where you want to go, and when, within that time period.
4. Some programs say you can get a certain type of ticket for a certain number of points or miles. The number of dollars you must spend on the bank credit card to get this type of ticket is often less that you must spend on a regular airline credit card. Usually there are no blackout dates on the ticket - if it is available, you can have it. Sometimes there is a dollar value cap on the ticket, and sometimes you can make up the difference.
5. Other programs give you a dollar credit towards a ticket for a defined number or points or miles. Beware of these types of programs. You are at the mercy of the bank's travel agent, who may or may not be able to buy the lowest price ticket for the flight you want. Ask if the agent has access to intent fares and consolidators. If no to either, avoid the program.
6. Some programs may prohibit you from buying a business class ticket, either via a dollar cap, or by simply not listing it as an award. This would be a deal breaker for me, as I do much of my travel on international overnight flights on which I need a business class ticket in order to sleep.
7. By purchasing airline tickets through a third party like this agent, Orbitz, Travelocity or Expedia, you take the risk of miscommunication between that company and the airline, with neither company taking responsibility for it. There have been numerous complaints on travel discussion boards regarding what happens if a flight is cancelled or changed so that a connection can no longer be made. The complaints involve either not being notified of the change, and/or neither company taking responsibility for rebooking you. See this discussion on Frommers, for example.

Below I have listed those some of my readers have insisted are worthwhile from their personal experience with them. I list them only as examples of what is available. I do not recommend any of them.

I do not plan to keep up with these offers or those similar to them. Read the current versions of the offers very carefully. You are on your own.

• American Express Blue Sky Credit Card.
• Quicken MasterCard with a travel rewards offer.
• Finance House Mastercard for residents of the UAE or those who work there and do transactions denominated in AED.
  • A very interesting no annual fee credit card that offers a 1% rebate on all of the transactions of the people you refer to the card (!).
  • This is not quite enough to motivate me to move there, but still...

Be sure to carefully read the terms and conditions.