Here's the problem: today, miles do not have value. They are not an asset, property, a currency, a security, a coupon, or a promise of future services. I do not own any frequent flyer miles, nor do I own any guarantee of any kind of value from the airlines. The constrains fliers in some ways, but it helps us in others.
If the IRS wants to head down the road of taxing miles, that's fine but it's a huge Pandora's box with many other consequences. If they have value, if they're an asset that I own, then I want the ability to buy and sell them on the open market. I want the airlines to be regulated as a bank or securities firm would, as they are their computer systems are the caretaker of my property. The programs themselves would need to be regulated, as they become in effect akin to a quasi-banking system of their own, whereby I use my property as a currency to buy services. Airlines, for their part, would need to invest a lot more money in this infrastructure and would have to account for miles totally differently.
Maybe all of this wouldn't come about immediately by legislation. Bits and pieces would come into play over time as the holders of miles sued for rights to control their own property. I wouldn't think it would take long, for example, for lawyers to sue on behalf of fliers to be able to sell their taxed property on an open exchange. Also should be easy to sue to prevent airlines from destroying the property via expiration dates or other means.
In other words, NO, I don't want any of this. As much as we might complain about devaluations, program changes, and seemingly one-sided policies that allow airlines to change our perceived value of miles over time, I still think the very existence of the programs absolutely depends on the nebulous nature of miles. If they legally become property that has value, it's just as bad for us as it is for the airlines. The whole game at that point is over.