No, but I guess e.g. physics.stackexchange.com or judaism.stackexchange.com benefits a lot from the SE internal links, and I guess for those smaller sites it is

No, but I guess e.g. physics.stackexchange.com or judaism.stackexchange.com benefits a lot from the SE internal links, and I guess for those smaller sites it is the main source of page rank. That is, if page rank still works like Google claims. I'm pretty convinced that there is a lot of manual curation going on. At least for popular terms and for the first page of results.