Oh, at last:
Google has added a line to Webmaster Guidelines to ask that Webmasters use a robots.txt file to disallow the indexation of search results pages:
Use robots.txt to prevent crawling of search results pages or other auto-generated pages that don’t add much value for users coming from search engines.
I really hope they programmatically find a way to beat these down.
Doing a search where the top results include anything from about.com is like getting up in the morning to discover that one of my cats horked in the laundry.