Who ever said that Google can only penalize other sites and can’t receive the same on its sites? As Google is far from perfect, it is also open to violating its own rules and guidelines. Take for example Google Japan, which employed paid blog entries to promote its new widget.
Google Japan commissioned Cyberbuzz to do an involuntary review (read: Google paid to get considered).
Google engineer Matt Cutts confirmed that such act was in violation of its policy not to tolerate buying links.
If CyberBuzz issued a nofollow on its links pointing to the widget page within Google Japan, it would have spared itself from the embarrassment and lower PageRank value. As Cutts states, “Google.co.jp PageRank is now ~5 instead of ~9. I expect that to remain for a while.”
Such act paints Google Japan as desperate enough to gather popularity and not setting a good example to others. If Google penalizes Google Japan, how much more for non-Google sites of same offense?