Well it does make since if you have mutiple gigs of space being taken up on
your servers because of data that hasn't been accessed in years.  Its better
to migrate that data to cheaper media.  Tape is still cheaper than disk
depending on who you are getting it from.  Also the labor involved in
extending disk drive resources are extensive across 100 home directory
servers and growing.  You might say why don't you get a SAN but if that SAN
is down for any reason my entired network is down.  HSM is a needed product
and it should work on highly used servers or infrequently accessed servers
as well.