It looks like that happens because the system that expands ranges into multiple queries is in front of the system that detects and blocks rapid clustered queries, so the query you entered looks is an enormous flood of queries in a very short time by the time it reeaches the abuse detection system.

Given the effect it would seem to have on load to execute queries of that magnitude, its not entirely unreasonable behavior although it would be better UX if the error returned distinguished the problem more clearly.

Google also does this if you proxy your requests through a cloud IP space. I proxy my Google searches through rackspace IPs and I was given a CAPTCHA on nearly every search.

I actually stopped using Google because of this (and privacy/creepiness issues). I switched to Bing. I have to say, Bing has gotten really good. When others saw me using it, they started using it too. Most of my office has switched now and people have stopped saying "google it" and started saying "bing it".

Clicky: https://www.google.com/search?q=he%20is%20"100000000..900000...

ahh, interesting.