a) unreliable (e.g. having opening hours a.k.a. intentional downtimes)
b) applying client side encryption a la https://privatebin.info
c) expire & purge the (encrypted) content quickly
would have mitigated your problem.
People distributing unmentionable content or using services for otherwise nefarious purposes are used to dealing with intermittent issues like that. It'll get rid of some but not all of them.
> b) applying client side encryption a la https://privatebin.info
> c) expire & purge the (encrypted) content quickly
If your site turns out to be being used by a group that is raided, this will not stop your services being confiscated and very thoroughly investigated. You might be legally in the clear, but it may cost you time and hassle (and potentially money if you need to take on the services of a lawyer to help prove you did not intentionally aid/abet).
Also an end-to-end encrypted solution like that might be rather attractive to users both illegal and otherwise, so be ready for a huge bandwidth bill if/when a sizable group latches onto it!
usually there's always one solution to get rid of all but that's prbly not what you think of.
So getting rid of some is what it's about, isn't it? And some more by another means.
Could crib notes from olden days and have a public/ subdirectory where files you drop in there are available read only to the public internet via separate endpoint.
Can also have a blind drop box that does the other direction (but does not allow the public to read).
That way you are read / write from all your devices, can publish to anyone, and can let anyone share things to you, you just don't facilitate anyone sharing to anyone.