Can get a lot of quality 1 way backlinks to the target site. It's pulled off by having some sister sites in the same niche, preferrably PR4 or higher. Such sites can be purchased easily to start with. Contact the owners of websites related to yours, and offer to give them a backlink from 1 or more aged sites with decent PR in return for a backlink from their site to your target site. This process can be automated. Always try to get backlinks from within content rather than pages with just links.