In my story about Google’s new content removal tools, I highlighted the fact that anyone can potentially wipe out the cached copy of a page, even if they aren’t the page’s author. To illustrate this, I was going to use as an example how the official George W. Bush page’s cached copy could get nixed. To my amazement, I found the cached copy was gone already. Had the White House decided to wipe out the cache, perhaps as damage control after the page started ranking for "failure" again recently? And why were Yahoo, Live.com and Ask still showing cached versions of that page? Was the White House — gasp! – cloaking only Google with a noarchive command?
Not at all! But it was a real mystery. As it turns out, some pages that Google revisits on a super-fast basis — pages that have dates next to them in the listings — might no longer have cached pages showing even when they should. Google says this is due to a bug they’re now checking on.
To illustrate this, look below:
Notice how any pages from the whitehouse.gov site with dates next to them do NOT have cached copies? And pages with dates DO have cached copies?
As I said, Google’s now aware of the issue and looking into it. And why do some pages get dates? Squeezing The Search Loaf: Finding Search Engine Freshness & Crawl Dates from me earlier this year explains that in much more depth.