I don't how much attribution the marketing of PageRank vs the actual effectiveness of PageRank (and undoubtedly other things never made public) deserves in the overall success of Google. I can't really think of a way in which we could easily come to such a conclusion either.

Ask Jeeves (or maybe Yahoo) tried a big "The Algorithm" marketing campaign and that clearly got them nowhere. I think if we're talking about marketing the "I'm feeling lucky" button was more of a boon to virality than PageRank.

Choosing PageRank was probably a slight lapse in integrity in my post, but undoubtedly there's been a whole bunch of other examples in Google's history which do fit the mold (GFS, MapReduce, Pregel, etc).