Google Trade Marked a new ranking factor called Trust Rank, which may start to be used in the algorithm. If you like to read all about it please visit TrustRank Algorithm. It's some what like Google Page Rank, but isn't fully automated. Instead it will use human editors to decide which web site ranks the highest in the new factor. Google has decided to do because all the Spam that's starting to show up a lot in Google search results.

Quote from Stanford - Web spam pages use various techniques to achieve higher-than-deserved rankings in a search engine's results. While human experts can identify spam, it is too expensive to manually evaluate a large number of pages. Instead, we propose techniques to semi-automatically separate reputable, good pages from spam. We first select a small set of seed pages to be evaluated by an expert. Once we manually identify the reputable seed pages, we use the link structure of the web to discover other pages that are likely to be good.

Trust Rank does seem like a good factor that can be better controlled and it will be easier to eliminate web sites that use Spam methods.