The init script of the vboxwebsrv from the ebuild mentioned above is broken. It tries to run vboxwebsrv from /opt/bin when it resides in /usr/bin . Reproducible: Always
On a related note (didn't think it was worth filing a separate bug). The vboxwebsrv init script for virtualbox-bin (3.1.0) tries to run vboxwebsrv from /usr/bin instead of /opt/bin.
Pop goes the rabbit - cool feature ;).
*** This bug has been marked as a duplicate of bug 298373 ***