Versioned USE="v4l2" has been removed from Portage. linux-headers-2.6.38 dropped support for video4linux 1.x and we have linux-headers-2.6.39 stable now.
USE="v4l" is now used for video4linux 2.x and/or libv4l userspace libraries. So anything using USE="v4l" for video4linux 1.x is a bug. There is no such thing anymore. For example, broken x11-misc/x11vnc here: http://bugs.gentoo.org/389079 - Samuli
