Why Kiln is based on Mercurial, and not other (D)VCS

Question

What were the reason for chosing Mercurial as a basis of FogCreek Kiln, a source control management system with tightly integrated code review, and FogBugz integration?

Answer 1

So now they add also git:

One of the biggest new features is Kiln Harmony, which lets you operate on Kiln repositories using either Git or Mercurial. So you can push changes to a Kiln repo using Git and then pull them using Mercurial. This means that you never have to decide whether you want to use Git or Mercurial.