I have a blog post in my head about this, and how links-as-currency is is a really broken system. Travel sites are a great example.<p>Companies like TripAdvisor literally have an army of 30-40 people whose sold job is link building and they measure how many they are able to generate per day. They literally calculate the "cost-per-link".<p>So, while they are not buying text links (which Google forbids), they ARE hurling manpower at linkbuilding in a systematic way.<p>So, if a link is a "vote" and Google is democratic, many SEO-centric sites like TripAdvisor are hiring people to drag voters to the ballot box and persuade them to vote for them.