Isn't the Downside with writing to a crystaline substance, it's a one and done kind of deal. No rewriting, no deleting, it's there forever.
possibly but if it costs 100 times less to produce, and you get an huge increase in size it dont really matter, it will cost almost nothing to just use a new one when the old one is full.
I'm fairly sure data would be able to be re-written. Otherwise they probably would never have pushed the development so far if there was such a large flaw.