I don't get why you're downvoted.

Toggling between two completely different newsfeeds based on screen size is not responsive—it's inconsistent.

If you don't agree, check out how different the old and the new feed are.

what if... there's a middle ground?

If facebook was set on using media queries, im sure they would have kept the same general design but just optimised layout and spacing for different screen sizes.

You guys are going down a pointless path of pedantry. The original attack suggested Facebook's sole reason for making the decision was advertising metrics. This person is saying that isn't true. I'm guessing the team running one of the top trafficked sites in the world is aware of media queries.

Yeah that was kind of my point... I got sucked in.

It doesn't have to look vastly different, it just has to look 'designed' for each screen size. This isn't a difficult problem... I'm wondering if responsive web design is a foreign concept within facebook. :\

Facebook.com isn't responsive (you'll see fixed width's, just check it out), so it does seem that responsive design is something they disregard purposefully.

Facebook cares too much about their performance to use responsive design.

People are used to different experiences on different devices. You can argue that they expect mobile and desktop versions to differ, but I can also argue that a 10-inch netbook is a very different device from a Retina MacBook.

Facebook already has an inconsistent experience. For instance, I've been viewing Facebook with this new design for a few days now, whereas other people are presumably still on the old one.

This is mostly a function of ramping up to Facebook scale and is a temporary inconsistency.