The major problems I see are one of two cases. Often just naive implementations run a filescan, run as fast as they can, the OS starts using more ram for cachi

The major problems I see are one of two cases. Often just naive implementations run a filescan, run as fast as they can, the OS starts using more ram for caching, then at some point applications need more ram. That triggers a reclaiming pages from cache, writing dirty pages, reading pages from the disk for the application, all while the scan is keeping the I/O pipeline full. The user observes this as a slow/laggy machine, and if you are unlucky enough to have a i7/i9 in a laptop often a fan running flat out. A second case is where a vendor offers "unlimited" backups for a flat price. This creates an incentive for the vendor to make an INCREDIBLY inefficient backup client that consumes substantial ram and CPU resources locally and minimal storage remotely. Typically this means that you aren't allowed to use more efficient clients, and have to use the vendors client. Here's looking at you crashplan.