Oh well, I am sure a lot of people will disagree (heck, there are even some people who find Linux on the Desktop a good idea :-) ).
Man, you're looking for a fight, aren't you? :)
Well, it's more a 'good old days' feelings than a real theory. Ie the biggest problem I see with 'Linux on everybody's Desktop' is that it's damaging for the community (due to the fact that the developper / user ratio is getting more and more skewed to the user side whereas 'in the golden days' anyone using Linux was a developper).
But well, this comes also from being in contact with Wine users everyday on #WineHQ :-)
Lionel