Would it be possible to create a plugin to warn a user if a page is being edited In a previous CMS we used (Processwire), one of the authors created a very useful plugin that would warn a user on an edit page that the page was currently being edited by another user.

I'm thinking this would be a useful addition, unless Craft's use of automatic versioning would somewhat rule out the risk of overwriting someone else's work?

Has anyone had any similar thoughts on the issue?

Thanks.
Inspired in part by Mats' detailed answer, I've written a plugin that does just this: MN Snitch

Enjoy!