The discussion, the heat and the hate here seem to be centered around the problem of freeloading, which is a moral argument. Yet most devs, including many participants here, are being paid for their Linux work. Making money is fundamentally not a moral motivation , but never the less, many feel the need to lambast others for "freeloading". Quite weird, isn't it?
So Ubuntu doesn't contribute as much as Redhat and Novel. How come? RH and Novel have lots of developers that contribute "upstream", Canonical doesn't. How come? RH has a *lot* of industry clients. A RH license sells in the range of a $1000 per seat. Is such an amount for a free OS frivolous or amoral? Now how much does an Ubuntu license cost? Does that fact give RH moral superiority over Canonical? I can't argue about Novel, since I don't know about them.
After many years I went to a LUG meeting recently and I was absolutely overwhelmed by the fact that half of the Linux enthusiasts (!) there had absolutely not _any_ command of the shell. Never ever touched a shell in their life. They were _not_ running RH of course and this feat was _not_ the achievement nor of Novel nor of RH.
The command of a shell and contributing back what "upstream" seems to percive as worthy could be correlated.
A last thing. Let's assume Mark Shuttleworth would get sick and tired of the flames, finally realize, that the other companies are in it for the money (are they?) and not for trying to serve humanity, shut his company down, fire all the Debian devs getting paid by him and thus /dev/null Ubuntu from this world. Would that be a desirable evolution? Weren't Canonical only freeloading anyway?
*t, from the shoulders of ancient giants
 It seems making money off Linux is a pill that has been swallowed a long time ago.