Anecdota, plural of data and all that, I know, but Google is able to find 15 years old posts from rather obscure french blogs.

https://encrypted.google.com/search?hl=fr&q=%22Dans%20mon%20...

https://encrypted.google.com/search?hl=fr&q=%22Eh%20bien%2C%...

BUT, interestingly enough, it can find posts for the very first months of the blog existence, but stays clueless for several posts dated a few years later. For instance, several exact strings from this page are not found by Google :

http://blog.smwhr.net/2003/10/