I'm 100% against making desktop computers thin though. Just make it 5x thicker and then cram anything you can inside that thing, and let there be plenty of space for the air to freely blow past GPU so it doesn't burn display. And while you're at it, you can even add some batteries so the iMac wouldn't turn off for a few hours if it's unplugged, or when the power is temporarily out (which results in lost user data, and if they were upgrading OS X, results in "very, very bad things").
It certainly makes sense to make a portable computer as thin and light as possible. But I never carry my iMac around and, sitting in front of it, I can't tell whether it is 5mm or 5cm.
I'd love for them to add a small battery to keep it running a half and hour on a power outage. Or upgradable RAM, disk, etc.
Really, I think the issue is they want them to be like televisions. Nobody upgrades a television, they just go out and buy a new own.
Have you considered that the reason might be to prevent iMacs from getting too loud?
Implies that "Fusion Drive" is already part of CoreStorage in 10.8.2. :)
That's exciting.
