Samizdata - 6:31 pm on May 21, 2011 (gmt 0)
they can get away with ignoring noarchive, because its not archived
They can get away with ignoring NOARCHIVE because it is proprietary and means whatever they say it means. Blekko and others can use it to mean something entirely different.
In my tests last year the preview image appeared to be cached on Google servers.