Imagine Linus Tarvolds stopped working on Linux before there was a foundation to take over because he did it just for fun and no one else wanted to take up the mantle? It's hard to say what the outcome from that would have been... maybe Google would have claimed it entirely and slowly shifted the license to something else?
I appreciate that people can create things for fun, and those things can be open-source, but if someone creates something because it's the right thing to do and not just about fun... well where do we stand now? Should they make it open-source but demand money? Should it be closed-source if the fun-factor is less than 80%? 50%?
Unless a small, dedicated team of capable people agree that your open-source project is worth preserving, allowing it to survive you as the founder, I question the validity of open-sourcing anything for fun unless you design the licence, and more, to enable you to walk away and/or get bored.
Would love to hear your thoughts.