We have many customers using SpiderOak to backup production servers, using various Windows flavors, Mac OS X, and Linux. Anything that you could backup with tapes, external hard drives, etc., SpiderOak can handle. We also have a number of partner IT support companies who resell SpiderOak as a value added backup service for their business customers.
For Exchange, MS SQL, Oracle, and so on, SpiderOak works best by backing up periodic archives or database dump files. This is the most common way that backups from these systems are created, and this is the way probably 95% of administrators arrange for backups.
To be very clear: SpiderOak is not designed for backing up a "hot" copy of Exchange's data files while Exchange is running and changing them. You could still use SpiderOak to archive the "hot" backups offsite as another product creates them.
SpiderOak is particularly well suited for storing a perpetual backup. For example, if you want to retain all previous versions of all files, all deleted items, and so on, SpiderOak's intensive de-duplication allows this to happen using minimal additional space. So for many business case scenarios, SpiderOak is ideal.