Other advantages of multiple partitions:
* If a partition fills up (say, a logging process starts spewing out
log entries by the millions), it only fills up that partition, rather
than "all" partitions, which provides less chance of file system
corruption/damage/lockups/etc.
* You can mount certain partitions read-only, such as / and /etc,
which helps to prevent tinkering or accidental changes to system files.
* During system maintenance, it's typically safer to mount only the
partitions you need to maintain/work with.
* It's easier to reconfigure a single partition or two than an entire
filesystem.
* There may be some slight enhancement of security from hackers to
have multiple partitions.
About the only disadvantages of multiple platforms:
* If you size them wrong to begin with (too small, and they'll fill
up; too large, and it's wasted disk space), it can be problematic to
resize them.
* It's a little more complex to set up (plan the sizes, names, make
sure /etc/fstab is correct, etc).