SEOcritique - 10:31 pm on Dec 25, 2006 (gmt 0)
As for identifying paid links that can affect the SERPs, Google cannot identify all paid links, but they can identify many. Some paid links have characteristics which give away, to varying degrees of ease, that they were purchased. Some link brokers actually publish their portfolios of the domains on which they place links. It's a matter of catch as can catch.