I just read Tim Bray's post, Google Memory Loss:

I think Google has stopped indexing the older parts of the Web. I think I can prove it. Google's competition is doing better. ...

They searched for exact strings from a 2006 post of theirs, and got no results, while searching on Bing and DuckDuckGo the post did come up. Since I also have posts from back then which get basically no traffic I wanted to see if I saw the same thing. Unfortunately I didn't.

I picked random phrases from five early blog posts and searched for them on Google:

• "I had been playing the accordion Davy lent to Rosie during winter break"

  

• "The language they're using is not that different from the one I wrote PlayGUI to use"

  

• "I've been playing a decent amount of music lately, mostly guitar and piano."

  

• "warm dry socks was the most important aspect of the festival"

  

• "This wouldn't be that bad, if it was not exactly what happened a year and a half ago."

  

Google found all five. For each one there were either 2 or 3 results: first my old post, then one or two from rssing.com which seems to do something with my rss feed.

Trying them with Bing, it also found all five of my posts, and ranked them first in four cases:

• 
• 
• 
• 

In the fifth case ("This wouldn't be that bad ...") it ranked a goodhousekeeping.com post higher, which had all the individual words but none of the phrases:

• 

Bing found more than Google, including results from Facebook and my rss feed, though their results were also much noisier due to finding many things that were not exact matches.

Overall this is some evidence that Bing can find more things than Google, but if Google is missing pages from its index it's not widespread enough to show up with these five queries.

(Disclosure: I work at Google, though not on search.)