I think it's a problem of reputation, actually. Google and Apple keep stuff online because they promised they would, and there would be backlash if they turned it off all of a sudden. There's nothing stopping a random, anonymous "filer" (like miner) from stopping the upload stream.
To go even further, if you orchestrate several miners carefully (maybe computationally) they can together perhaps stop people from accessing certain files.
To go even further, if you orchestrate several miners carefully (maybe computationally) they can together perhaps stop people from accessing certain files.