Hello,
In a shared storage environment is their anything to stop being able to mount the same filesystem on two hosts by accident, a flag being set or something on the storage?
If it did happen would one of the hosts panic?
If you are talking about fibre attached SAN storage then this can be done in the fibre switch (e.g. Brocade SAN Switch).
What storage are you using and how is it attached?
ZFS will complain if you try and mount a file system twice.
UFS won't put out any messages if multiple hosts mount the same file system, and I assume it could panic your host if more than one host were to write to it at the same time.
If you're concerned about multiple hosts accessing your file systems, you could mask LUNs on your at the switch (as noted above) or at the storage itself, depending on your configuration.