Correct. Not to mention that in order to pay back your debt (or get paid back) you have to find another trip for exactly the same amount of miles to fly with the said companion. I guess it would be quite difficult to find such dates/destinations within a reasonable timeframe, especially if M&M decides to "enhance" the program with new rules and new mileage levels in the meantime.

And then there's that issue of trust. How would you even know if you will get paid back. Maybe your companion decides that his reduced "fare" was an unlimited overdraft that has not to be repaid. After all, quite a few FTers seem to share such a peculiar view.

And what if your companion has an emergency, hence needs to change a flight, but you can't follow that change for whatever reason (or maybe there's only one award seat left on the new plane)? This means that the companion has to buy am expensive oneway award or even a paid ticket. Will he still pay you back? Or will he simply disappear? After all, he already paid more than he bargained for, so he might stop answering or e-mails and calls. Alternatively, he could simply keep telling you that he can't fly with you on this or that date, no matter what dates or destinations you present to him. Another form of unlimited overdraft.