The current use of backlinks is quite easily manipulated, and Google knows this. So why would they keep this business model if it is flawed? Simply put, they won’t. We can expect to see changes soon that make the simple method of having backlinks from high PR sites nearly useless.
The importance of simply buying mass backlinks in general is going to diminish completely. You might be saying “this is old news” right about now, but it’s not. The value is no longer going to be valued on the basic principle of your links existing on other websites, so having a footer link on a PR8 page isn’t going to matter very much.
What will matter though, is all of those links that you have in more “important” areas of websites. You will actually be better off having a link that gets click throughs on a page that is PR3 than you would be by having a footer link that gets no clicks on a PR8 website.
So what is Google going to do instead of track the number of backlinks to your site? They will actually be tracking all of the clicks through the link, and will determine each website’s relevance based on that… just like they already to with AdWords.
In case you aren’t familiar with how AdWords works, Google ranks the ads based on factors that are more important than just bid price. They actually track click throughs as well and take the bid price x click throughs to determine the advertiser which they are making the most money, and place them on top. For example, if website A gets 10 clicks at $1.00 per click from 100 impressions and website B gets 25 clicks at $0.50 per click from 100 impressions, Google will place website B above website A. Website A is generating $10 in revenue, but website B is generating $12.50 in revenue… all from the same number of impressions!
So to conclude, Google will be changing their search engine rankings to reflect the same type of quality that their Adwords system has. Expect to see major changes between December 2006 and March 2007.