On a recent flight on p.s. in "Pee" class, the FA and I were chatting about the manifest. There were several people on there who's status designators said only "Mileage Plus". She told me that that meant they were "free upgrades from cheap fares". I told her that no, it meant they weren't even elite, and that that meant they probably paid full fare. Again, dumbfounded.
I resemble that last scenario... Even though I don't have status (yet) and my company pays for economy only, unless it's overseas travel, I have _paid_ for own my upgrades to get out of E- since I am tall and can't stand much more than 2 hours back there. Luckily I have had mostly good experiences with the FA's but if they thought I was sitting up there for "free" they are sorely mistaken.