Substantial commitment is not necessary in practice. Joining the private beta of gaming.stackexchange.com required me to commit, but the site turned out to have

Substantial commitment is not necessary in practice. Joining the private beta of gaming.stackexchange.com required me to commit, but the site turned out to have a high XBox 360 and (surprisingly) Dwarf Fortress to everything else ratio and I have not returned with any enthusiasm. I've outgrown games perhaps, but committing didn't require anything. Maybe if it had cost me 1000 Stack Overflow reputation points I would have thought twice about signing up? If it did cost that much, it would be a high barrier to entry for non-programmer-non-stackoverflowers and the site would get less people committing (resulting in the "ghost town" effect).