Welcome to the upgrade auction!

I recently travelled to Los Angeles on Air New Zealand and had my first taste of their new upgrade auction system. As I was confirming my seat online, I was invited to enter an auction for an upgrade by entering an amount I was prepared to pay. Actually, let me clarify that: Air New Zealand clearly pointed out no money would be taken, unless my bid was accepted.So, faced with pleasant prospect of perhaps crossing the Atlantic in the lap of luxury, I threw in a figure just for the hell of it. Of course, my generous offer was ultimately politely declined but it was an interesting experience, and begs the question:is the end of the road for free upgrades?
This ingenious auction system, which incidentally has been embraced by a number of major carriers including Etihad and Virgin,is down to PlusGrade, a US based software company which manages each auction via web pages branded with airline livery.
The plus side for airlines is they get additional money for otherwise potentially empty seats, and PlusGrade only get rewarded through money generated by the auction. So, a win win then. But is it also a  win for passengers?
I suspect that in no time there will be web postings detailing the amounts people have paid for their winning upgrades and that of course will lead to resentment in other quarters from passengers who missed out.
It can only end in tears I suspect.
What do you think?  What would you pay?