I was not referring to current law, which I think you are.

I was referring to the attempt a few years ago to make FF miles taxable, which was thwarted by the inability to assign an exact determinable value.

What I meant was not that it'd be taxable from day one, but it could allow this past attempt to make FF miles taxable to be revived and succeed (in the case of RR 2.0 points, if RR 2.0 points had an exact value).

A rebate? If you are allowed to buy them on a website, now is that a rebate???

You cannot buy extra cashback from a cashback card, so that's why it's a rebate. But miles and points can be different, if you can get them through ways other than rebate-like, which includes purchasing them outright. They are for all intents and purposes "currencies", because you can earn them, save them, and spend them, just not at exact determined rates like conventional money.

In case you're not aware, miles are already taxed in the specific case of sweepstakes which award a large amount of miles. I never enter sweepstakes for big miles prizes, because I'm afriad I'd win, and then be liable for taxes I couldn't afford (owed way before I could use most of the miles). In that case, there's some somewhat artbitrary "average" redemption value that the airline assigns as the value of the sweepstakes award (luckily, it's not based on redemption on business or first class international flights, but on the average redemption most "kettles" do).