Comment 11 for bug 1124250

running:
sudo sysctl kernel.keys.root_maxkeys=1000
sudo sysctl kernel.keys.maxkeys=1000

fixes the issue for me to some extent. I still have some files with 4294967294 instead of nobody or nogroup.

I only see the problem on one ldap and nfsv4 client running ubuntu 14.04 LTS (as a testbed). My other servers are running 12.04 and don't have the issue. They don't seem to be using these keys at all. Is idmaping enabled by default on 14.04 where it wasn't in 12.04?