We have a few clients with teams of hundreds of writers and contributors. It's a real task to make sure nobody uploads 8 MB 4200 x 3700 images to their website.
When they do, a couple of things happen: the site slows down. Occasionally somebody manages to put the original in the post and their bandwidth goes through the roof.
While it's possible to put a hard upload limit in which defeats the heavy uploads, the errors create a lot of unnecessary administrative overhead.
Imagine that someone created a plugin which would resize huge images to the maximum size used on your site.
Well someone just did.
Try verysimple's Imsanity.
Weird but very cool branding.