goodroi - 11:39 am on Dec 29, 2010 (gmt 0)
Google has tried and will continue to try to identify paid links and to devalue them. It is possible to find some paid links that have yet to be devalued. It is also possible to find active paid links that are no longer passing any significant link juice.
I recently reviewed a website and cut their paid link monthly budget from $1000 to $50 and they maintained their rankings and traffic levels. It was a good example of how paid links that gave a ranking boost when they were originally bought might not be helpful anymore.