[haylem]

I had a few in mind when I was back in uni and hosting and cloud storage prices were still up.

I hadn't thought of reddit, as the abuse would be clearly visible, but I had used back then that Gmail Drive some guy had implemented using emails for storage, and it led me to think a lot of the Google Systems had non-obvious "unlimited" storage options.

For instance, I don't know if that's still the case, but Google Calendar surely seemed pretty fit for abuse: while calendar entries were limited in size, you could have as many as you wanted. And calendars can be private, so it's even better.

The problem with such systems will be the integrity of your data, when you start being forced to chunk things up. If they change one thing under your feet, you're a bit screwed. Also you have to detect all the undocumented pitfalls (e.g. forbidden characters in an edit field).