It's as much of a concern as you make it, e.g. by storing redundant keys or key shards elsewhere, and it can be a strength as well as a weakness. Inability to

It's as much of a concern as you make it, e.g. by storing redundant keys or key shards elsewhere, and it can be a strength as well as a weakness. Inability to delete or destroy data is an increasing problem. If you replicate or back up your data, how do you ensure all the copies are gone? If you store it on an SSD, how do you ensure that wear-leveling and remapping hasn't caused the physical blocks containing that data to remain intact? Being able to throw away the key and be sure that nobody can get at the data again can be quite nice. The important thing is that you get to control those keys and therefore the persistence of that data.