The system did not and could not store information permanently, if it did it would fill up, which is a non-starter when it depends on people volunteering their hard disk space.
I don't know about going ballistic, but since this issue is addressed directly in their papers (section 3.4 of the linked paper) I can see us getting irritated by people re-asking questions that have already been answered.
Hell, most people don't read FAQs either.
As for "can't" that's not accurate. You can certainly prevent old data from being pushed out, by returning an error on insertion of new data if there's no free space. That's how many other storage systems (e.g. every filesystem ever) work. While it's true that you can't fully protect against a reduction of capacity when nodes go offline, that's a very different issue. Freenet being cache-like rather than storage-like was a decision of convenience, not a technical necessity.
Freenet is designed for sharing information, not archiving it. You can't have both.
When it was still relevant, i.e. a long time ago.