A big problem that some have mentioned but I don't think gets emphasized enough is that both airlines and banks have gotten less competitive and more oligopolistic at the top level during this time when you get the explosion of blogs and the online tools have gotten better. So you have not only a lot more wannabes in the game, but a much worse playing field.

With the banks you get exclusive arrangements with mileage-earning cards, so only the top behemoths are in at that level. Others get to do points-based, which can have some advantages but aren't so churn-able. With banks in general you have something like the top 6 controlling 70% of assets, or some lopsided number like that.

With airlines you've got the US3 that just doesn't care as much about competing anymore and treats their FFers like the European monopoly flag carriers long treated theirs. The main competition in airlines, such as it is, is with ULCCs, and some of those are like Spirit in that they have a pretty uninspired FF program and hate the idea of elite perks that could decrease the charge-for-everything fee revenue. The ULCCs can be spoilers with "capacity discipline" (F9's ATL-SLC nonstop a perfect example...did a RT on that last year at $54 at a particularly low time). OTOH, they generally don't have enough planes or frequency yet, And DL has not been matching F9 or NK like it used to match WN.