[sparkzilla]

Getting free contributions works for Wikipedia because it is not a business, has no ads and it's supported by donations. And because people get ego value from getting their contributions on a large, popular site. However, if the intention is to use free content to make the owners (and VCs) rich, then I am not sure that is a sustainable business model in the long term.

[tyang]

Quora and Yelp are for profit.

[sparkzilla]

Yes, and their models are unsustainable. I wouldn't be an investor in any company that uses free labor.