A really cool concept, and I even tried to set up an instance. But it has no practical interest if you're trying to search the web : it won't return a result before several seconds (30-50 s), it will resurn 0 page for some searches that would return many pages on any major search engine, etc... So I love the FOSS and peer-to-peer approach, but It's not useful for now, and trying to contribute is not easy either, as configuring an instance is quite complicated (installation is easy, but configuration is hard). That said, I'd love Yacy to become more of a thing...