Every company I've ever worked at (save one) had projectors in conference rooms, but no permanent computer hooked up to it. The meeting organizer would have to set up a web conference in something, and then people would share their Desktop, and whoever the presenter at the moment was would plug in their laptop.
And then the guy forgot his power cord, and can't project for the whole meeting.
And then the other guy forgot his Mac's VGA converter.
And then some other guy has a Mac VGA converter, but it's the old one, not the new one.
And then the guy's Windows box for some reason will not show video on the second monitor.
And the file he needed was on his desktop, not his laptop, and does anyone have a USB key?
And now Windows is rebooting and you can't turn off the power, because it's installing updates.
I think a permanent ChromeOS-based computer plugged in to the projector makes a TON of sense. I've also drunk the Google Docs kool-aid, so YMMV.
EDIT: Oh, and then because the projector was sharing his desktop, we get to see a ton of instant messages. Some of them from his wife. If instead you were doing a Hangout on a collaborative Google Doc, you wouldn't see that.