A porn site ranked first in Google Scholar

I was just wondering about how Google Scholar works the other day. It does seem like they can't just have a manual list of sources, because in many cases, it picks up papers from the websites of their authors, not just from large sources like the ACM or the NIPS proceedings or whatever. But even if you are able to pick out research papers when you crawl the whole web, and get author/title/citation information out of them, how do you rank them? In particular, they have citation links between papers -- but presumably any paper can only cite to older papers, so papers form a DAG, where it seems like PageRank shouldn't really work (because the most 'authoritative' papers would end up being old ones).

I'd say it's lacking in originality and doesn't contribute anything particularly new to the field. I doubt it will attract many citations. No wonder they couldn't get it published in a decent journal.

(Narrowly avoided: a "seminal contribution" pun)