I just updated sys-apps/baselayout from 22.214.171.124 to 1.12.13.
At the next reboot, init stopped after a second, yelling something about udev, asking me to press Ctrl-D or give rootpw.
My / is on a md raid1. It seems, udev was just not finding it --> nothing worked anymore.
I resolved the problem by downgrading baselayout again, that left me with some config files with modification time in the future, but a working system.
I cannot really give more input here, because I had to get my system back up, but I suggest to mask sys-apps/baselayout-1.12.13 again really really fast...
Steps to Reproduce:
1. emerge =sys-apps/baselayout-1.12.13
*** This bug has been marked as a duplicate of bug 291916 ***