A large proportion of historic usenet posts are archived and remain freely available today. Didn't google end up with one of the larger commercial archives? So that "stupid stuff" is still around unless it got deleted at the time (and wasn't archived first).

New uploads to github are constantly being scanned by both benevolent and malicious actors for secrets that were inadvertently checked in. It's far too late by the time you notice and delete it.

This P2P system doesn't appear to introduce any new problems that aren't already widespread.