Bingo. FF program decisions are hard to evaluate based on a snapshot, because they are unsustainable without major change (primarily ongoing devaluation).

The other great point was that miles earned from flying are often not correlated with profit generated for the airline. For credit card spending, we can at least be sure that the miles correspond to profit.

Virgin's Elevate program may point the way to the future here. Its earnings are tied directly to ticket price, with a class of service multiplier. Redemption is tied to cash ticket price as well. The result is a boring program because we can't game it for higher value.