Assuming OS X 10.8.2
Aim for one or both of the following. If you like, set aside a copy of the one that includes the incident.
/private/var/log/com.apple.launchd/launchd-shutdown.system.log
/private/var/log/com.apple.launchd/launchd-shutdown.system.log.1
If corruption is a possibility, I'd begin with a scrub of the pool to which that zfsvfs_teardown related.
http://www.google.co.uk/search?hl=en&q= ... 20vnode%22 finds a few things. Adding +ZFS to the query finds nothing … as the benefits of timely review of launchd-shutdown.system.log may be not widely realised, it may be that people are simply not reporting (in public) relevant details.