I have been thinking about link building and I would like to run an idea by you all about building a link network among SEOs. Getting in-content relevant links from quality websites is very difficult and expensive as you all know, but what about a Link network of websites that link to each other. This would not be link-exchanges per say. Each website within the network would provide a in-content link to another relevant website within the network, but no 2 sites would "exchange" links within the network. Every site you provide a link to, would not link back to you but link to another relevant site in the network, and because each site is providing a link from the site they are promoting, you know the links are high quality. I think it would be pretty easy to dominate many niches with say 30 high quality, in-content, relevant links. Links would not all have the same keywords as that is an obvious sign of abuse from google, but they would all come from a relevant niche.
It's been done many times before. The biggest was called Link Vault (from memory). They work for a while, but eventually, you get penalised. Policing the quality of the sites in the network is the biggest issue.