These two hires are concerning AMD's recent open-source hiring efforts. Some developers and I have known who these hires were, but now Alex Deucher has publicly mentioned them. Michel and Christian should be familiar names if you ready many Phoronix articles, but here's a brief description on each of them.
Michel Dänzer: Michel is joining AMD from VMware. Michel is one of the well known VMware developers that was originally with Tungsten Graphics and has worked on the various parts of the stack, in particular Mesa and Gallium3D. Prior to Tungsten Graphics, he was an ATI employee several years ago. Before leaving ATI to return back to Switzerland, Dänzer worked on Matthew Tippett's team doing the Catalyst Linux driver. It's particularly good seeing Michel come back to ATI/AMD.
Christian König: Christian is the German developer that first introduced open-source HDMI audio support for the Radeon HD driver and then later to the xf86-video-ati DDX and then the Radeon DRM driver. Christian was the community developer that had to do some reverse-engineering to originally get this HDMI audio support going. More recently, Christian's been working on video playback improvements to Gallium3D. He brought XvMC support to the R600g driver and then most recently turned to working on VDPAU support for Radeon Gallium3D.