I have spent a lot of time naming different people using the Faces feature and tonight when I opened the program there is no folder of my wife and all of the photos with her name have another persons names on them!!!! WOW, it has actually combined hundreds of photos into different named folders. For example if someone had the name Shannon, it changed the name to Torie and combined all the Shannon and Torie pictures using the Torie name on all of the photos. The folder for Shannon is now gone. It did this to about 8 or 10 folders. What a mess. I guess I am not the only one there is thread going on in the Apple Discussions. My suggestion is not to put too much work into naming your Faces until this bug is solved.
http://discussions.apple.com/thread.jspa?threadID=1884890
http://discussions.apple.com/thread.jspa?threadID=1884890