This happens at my installation too (getent gives ~10k registered users). When logging with a local user and the network disabled all is ok, but if the network is enabled the panel freezes on login and the fast-user-switch-applet task runs at 100%. Now, I can't remove the package as ubuntu-desktop depends on it, and while I've removed the applet from the default environment, there is no easy way to remove it from users desktops automatically on login...
This happens at my installation too (getent gives ~10k registered users). When logging with a local user and the network disabled all is ok, but if the network is enabled the panel freezes on login and the fast-user- switch- applet task runs at 100%. Now, I can't remove the package as ubuntu-desktop depends on it, and while I've removed the applet from the default environment, there is no easy way to remove it from users desktops automatically on login...