Miles cost money, MCI and AT&T are paying for those FF miles they give you. Long distance rates are falling, and revenue is shrinking for the telcos. I would expect to see more plans that give great prices and no mileage down the road on a more wide scale basis. Only top rate paying customers and large monthly billers will benifit from FF mileage.
How much is FF mileage worth. Calling cards from MCI & AT&T are usually at least 70% higher then a good pre-paid card.