Jeff Atwood, one of the co-founders of Stack Overflow recently wrote a blog post Trouble In the House of Google, where he noted that several sites that scrape Stack Overflow content (which Stack Overflow's CC-BY-SA license permits) appear higher in Google's search rankings than the original Stack Overflow pages . When Stack Overflow chose the CC-BY-SA license they made the assumption that:Jeff Atwood's post goes on to argue that something

Nice paper by Robert Huber and Jens Klump has appeared in Computers & Geosciences entitled "Charting taxonomic knowledge through ontologies and ranking algorithms" (doi:10.1016/j.cageo.2008.02.016). The paper is not open access, but you can get some background from the post How TaxonRank works. Here's the abstract.

This will probably tempt fate, but I've an invited manuscript in review for Briefings in Bioinformatics on the topic of identifiers in biodiversity informatics.

Came across the paper "Using incomplete citation data for MEDLINE results ranking" (pmid:16779053, fulltext available in PMC .The authors applied PageRank (the algorithm Google use to rank search results) to papers in MEDLINE and found that PageRank is robust to information loss. In other words, even if a citation database is incomplete it will do a good job of ranking results.