Most mileage programs are actually an asset to the company and not a liability. Airlines earn revenue through partners by selling miles to CC companies and other businesses at 1.5-2 cents per mile. Also, you will notice that when companies go bankrupt they end up selling their mileage programs even including all the built-in liabilities.

And with the majors there seems to be a divide of ones that are making it EASIER to get elite status (UA, AA, US, and NW) and those that are making it HARDER to get elite status (CO, DL). But in general, I think its getting easier since elite status keeps them from losing customers. In such a competitive market, mileage bonuses are getting bigger than ever. As a result, its been harder to redeem miles and get elite-status benefits such as upgrades.

I don't think JetBlue really needs a great FF program at this point, because they are the new buzz-word in the airline industry and they get enough good press to sustain good business. But to draw the frequent business traveller, a good FF program would be helpful.