On the KDE Wiki there is an article about digital asset management with Digikam. It is quite long and covers general DAM topics as well and their realization with Digikam. From image downloading from cameras through sorting, rating, captioning, geotagging and cataloging, to archiving and backing up. It discusses the features of back-up medias and the main causes of data loss as well.
It covers both theory and practice, and is an interesting article to read, not only for Digikam users.