Thanks for the many & varied responses.  It seems there are indeed
differing opinions, but then every site is not the same.

Can anybody see any merit in the following arguments.

Granted it ignores the support costs (which are higher for lots of
small ADSM clients), it also ignores the cost of individual PC hard
disks (we already have them) and it ignores the cost of actually
storing the data on ADSM (which is the same in both cases anyway).

What does it cost in diskspace on the server compared to client licenses.

Say 1GB = $1,000 (of server storage!)  =>  100 MB = $100 ~ cost of 1
license (roughly)

Therefore I can spend the $100 on central storage space, which will
allow me 100 MB of storage (per person), or I can buy 1 client license
& backup the whole 10GB of data on the local PC harddisk!

Therefore as long as you are using that 1 client license to backup a
significant amount of data (say more than 100MB), then you are better
off spending the money on a client license rather than central storage.

Try plotting a graph of Data volume vs cost.  For the central storage
case the cost is propotional to the Data volume, while for the client
license it is a flat fee (depending on number of client licenses).

Obviously this only applies to data you are not sharing with other
people, which in our case is the bulk of the data (eg. individual mail
files).  Leave the data to be shared on the LAN servers.  It also
happens to be the personal data that incurs the highest IO rates which
is best moved off the LAN for performance reasons.

So for people with small data storage requirements, keep it centrally,
while people with large storage requirements it is more cost effective
to keep it locally and backup to ADSM.  Exactly where the cutover point
is, would need detailed study & will vary from site to site, but I
expect 100MB is not too far off.

I don't think the issues about data management really apply.  This
really needs to be done by whoever owns the data, and whether it is
sitting on a local hard disk or a LAN server doesn't really make any
difference.  Obviously there is potential for data volumes to grow
enormously as people fill up their local hard disks (they usually run
into quota restrictions on a server).  The best way to manage this is
to charge the users for the privilege of storing their data on ADSM,
expose the top users to management scrutiny (same as phone bills), and
let nature take it's course.  In my opinion it is not an IT job to tell
users how much data they need to do their job, but rather to provide
the tools at the right price to let them get on with it.

Have I just answered my own question???  Thanks for allowing me to
indulge myself.