This has been touched on before in several threads - look under Amex (who let you buy elite with their new card), Starwood (who let you buy gold membership), search for pudding and you will find a myriad of reactions, and I am sure that I am missing a lot of threads.

It is not a matter of simple buyer vs. flyer, many frequent flyers will also take advantage of credit cards, MCI, healthy choice, etc. I fly a lot and also collect substantial miles through means other than flights. For example I have rarely flown British Airways, but have redeemed a business class ticket with them to the opposite side of the globe. Welcome to the new world of FF programs. I suspect that a lot of us fall in the same category. So, it would not bother me if a flyer sitting next to me had earned miles by flying, or taken a couple of extra flights near year end just to get miles/status, or bought the miles/status by stationary means.