How is it screwing up? How are they supposed to run a search engine without prioritizing? "Here's 30000 results, we've randomly sorted them for you"?
Because only a handful of companies can issue certificates.
Fair enough.
The principles behind PageRank are based on unbiased reputation, and provide for a good ranking system (spammers aside). Whatever's thrown on top needs to be carefully considered not to enforce biases towards any group in particular.
Maybe quality of content? If the best info gets buried because they can't afford a cert or don't have a need for one then this hurts the Internet.