This is said a lot, and I have to disagree. The content I serve to someone on a large monitor is going to be different than what I serve up to someone on mobile because I understand what the different needs and desires are for the user groups on each device, not because anything else is noise and filler.

Not quite. It's like limiting the dashboard of a smaller car.

For instance, mobile users can do without the "Latest Posts" sidebar on a forum, but the users preferred it on the desktop. You'd probably remove most of the Twitter Bootstrap topbar links from the mobile version because they'd scrunch up and get in the way, but that doesn't mean having the "Quickstart Guide" link convenient on the desktop version.

There's nothing glorious about not taking advantage of larger screen real estate to make your website more usable, convenient, and feature-accessible to your users. It's the difference between good and bad design.

Not really. I might prioritise the 'Find us' page and the staff biographies in the mobile site - bring them front and centre in navigation. By contrast, case studies are unlikely to be so important to the mobile user, but that doesn't mean that someone evaluating a company isn't interested in them.