We now see programs that allow users to add comments to their digitized materials, like the Maine Memory Network (example). Allowing users to add comments is a great way of including their knowledge in the collection. Undoubtedly there will be a few people -- with long memories -- that would enjoy adding what they remember. (Genealogists, especially could have a heyday.)
Although it may sound frightening, providing a way for users to comment on all types of materials could be useful in ensuring that information -- unknown to the group that mounted the collection -- is not forgotten. One of the best places for this might be in allowing users to add comments to materials that document history, whether it be the history of a family, community, a product, or a company. What tidbits -- lost from the records -- could be added?!
As I think about this, I think of companies that are likely digitized their old records in order to create a knowledge management system. It is likely that they are digitizing the official documents kept as part of their document retention program. But those documents may not contain the "rest of the story" and the unsanitized version of what occurred during the product's life-cycle, for example. There could be comments added that would ensure that the company understood truly how it succeeded and reminded the company of what it shouldn't do again.
Would you want to approve comments that are submitted? Yes and you would want the right to not display any that were deemed inappropriate. Notice I didn't say delete, since an inappropriate comment could still have information that you may want to retain. We know that some people could submitted damaging and incorrect comments, so you need to be able to deal with that. Any program that is allowing people to add comments should have public statement about how they will deal with inappropriate or erroneous comments.
Finally, comments are useless if no one acts on them. If you accept comments, have someone review them and see what can be used from them. Who knows what you will find!
Technorati tag: institutional repository, web 2.0