[petertodd]

> making it impossible to reliably delete material

That said, SSD's have improved the situation a lot with TRIM. While previously deleting a file wouldn't actually destroy any data until it was overwritten. With TRIM in most cases for files more than a few KB almost all the data will be physically destroyed soon after TRIM is called. It depends on settings. But that's commonly either immediately, or about once a day (the default on Android).

If you read the forensics literature TRIM has caused them enormous problems by radically reducing the amount of data available.