orphan miles are gravy to airlines. They mean nothing because they will never be redeemed.

Loyal frequent travellers, the profit mainstay of airlines, don't have orphan miles. Only lousy airline customers have them. By definition, orphan mileage customers are not loyal and don't fly frequently so they are not responsive to loyalty programs and hence to be basically written off by the airlines' marketing programs.

A bigger question is, How do airline loyalty programs affect frequent flyer's decisions to use one airline over another?

I believe the greatest influence on loyalty is frequency of service in a given flyer's market. I am a UA loyal person because I can go to IAD and get many direct flights. How much do loyalty programs influence me?

Would I go to AA if they offered me a superb loyalty program by virtue of the fact that they want to win my business and know they have to offer me a "better deal" than UA? For instance, if they offered me triple miles out of IAD (but I always have to connect in ORD or DFW) would they win my business, would this be enough to counter the inconvenience? What about quadruple miles? What about unlimited free upgrades on cheap fares? Would that sway me? Would it be profitable for airlines (and other businesses) to entice hard-to-win-over but potentially profitable accounts through offering selectively higher loyalty bonuses? Huh? (Sorry, I had to add that)

I'd love to see some thinking on that!