I was browsing Stack Overflow with my iPad and 15 minutes ago it started showing the mobile version instead of the full one. Clicking on the "full version" link at the bottom of the page does not help as it still shows the mobile version. Is this a permanent change? (hope not)
This is fixed in the build currently rolling out.
Essentially both we and the MVC team came around to the same naming convention for our views, and the implementations co-exist so well together that we didn't catch* you couldn't switch back to the Desktop view from a mobile device.
Fix is, somewhat humorously, to just have MVC4 treat every device as a Desktop and let our existing code handle detecting mobile devices.
*MVC4 also considers the iPad a mobile device while we don't, but that's a minor detail.