When I booked a *A award at United's Ireland call-center last year, I only had to send them a fax confirming that I allow the pax to travel on my miles. Obviously that's a perk for MP members from abroad, where airports with UA ticket offices can be a rather rare occurance.

Unfortunately, the Ireland call-center has since closed, and I wouldn't trust UA's Poland/India call-centers (which replaced it) with even the most simple award booking.

With M&M, anything goes: Not only can you use your miles to upgrade a friend or make award bookings, you can also upgrade yourself (or anybody else) or book awards for yourself (or anybody else) using somebody else's M&M account. All you need is his membership number and his PIN. Basically, person A can book an award for person B using miles from person C's account, and each of them can have different names and addresses. Or even upgrade one way of B's trip with person C's miles, and the other way with person D's miles. Of course, doing so with accounts that are spread around the world might end up in some auditing.