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I have seen in some instances where sites will add iframes if they have to use duplicate content, then nofollow the iframes, and tell the robot file to ignore them so they aren't analyzed.  It works actually, but it's sloppy code having a iframe on every page sometimes multiple.  Or at least it is to me for that purpose, but I guess it's better than getting penalized for dup content. Have a great night. Matthew Boley

According to the updated Google Webmaster Guidelines, widget links and frankly all sorts of paid/advertising links are ONLY accepted if they contain the nofollow attribute. Here's the exact paragraph that clarifies this issue: "Note that PPC (pay-per-click) advertising links that don’t pass PageRank to the buyer of the ad do not violate our guidelines." -according to Google, almost anything that passes PageRank is suspected of violating their guidelines. (source)