In the UNIX environment it is a good idea to have multiple partitions for different root-level directories such as /usr, /var, /home, etc. It is transparent to whomever is using the system, but having multiple file systems allows for multiple points of failure instead of just one.
I think it could be a little tricky doing it with OS X, but the reasoning behind it is sound.
I think it could be a little tricky doing it with OS X, but the reasoning behind it is sound.