Page rank was very useful when they started, 19 years ago. It was killed by their own success as normal people stopped posting link sites, and bad actors added their own.
The people that I know at MS and Yahoo told me that Page Rank was never as good as meta-documents. And meta-documents was more than sufficient to explain the improvement in relevance.
Of course this is anecdotal and I would be happy to see evidence to the contrary.
Of course this is anecdotal and I would be happy to see evidence to the contrary.