A Google Webmaster Help thread has a very revealing, at least to me, post from a Googler about how the Google Algorithm works.

Many people feel the Google Algorithm is a single, but large algorithm. But those who have been doing this for a while know that Google has many algorithms. When I covered the SEO 101 session, which is kinda funny, but I wanted to listen to Bruce Clay, it can be refreshing. I fed Bruce a question, that I knew he’d love to answer, about the Google algorithm. In short, I said Bing said they have over 1000 ranking factors, but Google said about 200 – what’s up with that. Bruce answered it like the pro he is and explained that “for a specific query, Google may use 200 or so factors, but they likely have thousands. but they use different algorithms for different search intent.” (paraphrasing)

That is spot on. For the first time that I’ve seen Google comment specifically about this.

JohnMu said in the Google Webmaster Help thread:

This was in response to why one webmaster was complaining he was hit by the May Day search quality algorithm change. John explained that when it first launched, the algorithm likely didn’t apply to his site, but as sites change, the algorithm will go out looking for matches and when it does, you might get a special look by that algorithm.

Again, this is likely not new to many seniored SEOs but it is always gravy to find this in the forums by a Googler.

Forum discussion at Google Webmaster Help.