This is good, but simplistic.
Firstly the downfall in the geocities-web came in many phases:
1. Spam Email Phase
2. Phishing / Nigerian phase
3. Popup phase
4. Autoplaying Flash/ActiveX phase
5. Pagerank phase (forums being ruined until rel=nofollow)
Now google, previously the main gateway to discovery, is pretty much useless for discovering new non-commercial content.
The way this could go away is only from a market shift; deleting your facebook won't bring back geocities. The fact is, if I had a geocities page it'd be undiscoverable due to pagerank, so I have no incentive to publish unless I have another avenue of attention (resume, Hn profile).
Can a non-commercial search engine ever exist? I suppose reddit/HN voting is one semi-successful method of content ranking...