I would think that it does not make sense that someone is legally required to split them in a divorce for these reasons:

1. They are not transferrable according to the rules of the program.

2. Their value is not easily able to be calculated. That is why the IRS has (thankfully) shyed from taxing them. You can use the value that the airlines uses in their accounting if you want, but that amounts to about $20 per 25k miles. Even if you have 1 million miles, that only amounts to $400 - hardly worth pursuing. On the other hand, there is the value that the airline sells them at, about 2.5+ cents per mile, but that is an amount that no one in the right mind would pay unless a small amount is needed for a threshold (and in even those cases, I still would not pay that amount). Since they were (probably) not purchased, that value cannot be used either.

Their value is, in this case, "in the value of the beholder (owner)" in how he uses them. For that reason, I do not see how one could legally attribute a value to them for division in a divorce.