The business case for Digital Asset Management does stack up if your internal operations are of a significant size, in other words that there are enough users accessing the system and this can be from a print and online production environment through traffic/production staff to account teams, and it is used!

It becomes more advantageous to those agencies offering a variety of services - full service agencies for instance. Assets may be used in many formats and more than once, in fact many times throughout the year.
Image files should definitely have key meta data in them, not just when they were shot, but by whom, for which client and in the case of images purchased from libraries what the IPR is, when/if it expires etc.

When considering a DAM (Digital Asset Management) solution many agencies think only of storing the assets for thier original purpose.

Take this example:

A Campaign running online (banners, email, website) and offline (outdoor, DM, Press) run by an agency. Different formats both for print and for online all have to be produced, then some of these will be amended to different formats and then revised and reprinted at a later date. All the assets are produced and filed. Working in silos the production dept will have their storage, the traffic dept will have theirs and possibly the account management team another - they may have file copies.

Then consider the client wants a yearly review of the work you have done for them - compiling all those peices of work could be very time intensive and utilise the time of someone from each department when it could well be performed by one individual with access to a good DAM.

or, you work in partnership with other companies to provide support services - you give them access, reducing your time

or, the client wants to present all the work you have done for them to their board.

or, you are asked to supply the final copy (text only) from that brochure you produced for them two year's ago and they need it today. Or, the copywriter needs to update from the last final copy for an updated version and doesn't want to rekey it all.

There are many solutions available and most of them have come down in price by a long way. You may decide to implement a low price off the shelf solution to start with to support the business case. What's important is that you involve every department in the agency as you'll be surprised just how useful these systems can be, providing you put the right implementation rules in place and that they are followed.

Lastly, consider whether it should be in-house or whether it should be outsourced. I would say that if you are using outsourcing for assets such as production and print/online, that you request that whoever you are using implements a DAM, which would reduce your overhead, assist in thier customer service to you and increase their offerings against the competition.

Peter