Matt Cutts states that purchased links or text links ads are detected and given no ranking value about 95% of the time. It could be that Google is closer to detecting 99% of paid links.
Google has created an all encompassing programming API that will allow webmasters to share social applications between services. Partners include MySpace.com, Beebo.com, Ning.com, Engage.com, Friendster.com, hi5.com, Hyves.com, imeem.com, LinkedIn.com, Oracle.com, orkut.com, Plaxo.com, Salesforce.com, SixApart.com, Tianji.com,