Compared to the invention of the Internet and/or the WWW, I'm of the opinion that calling Google (the search engine) or PageRank (the algorithm) one of the Great Inventions in Human History (and capitalizing it) is too far-fetched. The first is an indexer for the former, and the latter is not so different from eigenvector centrality, with the added spice of directed random walks.

I do believe that the Internet/WWW is one of our greatest inventions, though, so this is just nit-picking. :)