This seems to be a Yosemite issue, not just 12" MacBooks.
I know various people over the last few months that have purchased new Macs and during setup (usually FileVault stage) have run into issues. These have been MacBook Airs, iMacs and MacBook Pro Retinas.
I know various people over the last few months that have purchased new Macs and during setup (usually FileVault stage) have run into issues. These have been MacBook Airs, iMacs and MacBook Pro Retinas.