After Canonical announced its new display manager Mir and presented their reasons, the X and Wayland developers were not happy.Wayland creator, Kristian Høgsberg, has posted on Google+ the link to the Mir wiki spec from Canonical and everyone, including X developers, started to tear it apart.
They were not upset because Canonical worked separately on a new display manager. The main reason was that Canonical has bashed their work and stated a lot of things that apparently were not true.
Kristian Høgsberg explained that a lot of the features Wayland was supposed to be lacking were in fact present and working on the current version.
If you have the time for a lengthy and interesting topic about Mir and Canonical's lack of experience in tackling such a complicated problem, you should check out the official Google+.