Examples:
* from https://www.google.com/#q=test to http://www.google.com/?nord=1#q=test
* from https://www.google.com/search?q=test to http://www.google.com/search?q=test&nord=1
Why would you switch from the encrypted version of Google to the non-encrypted version? I can find a few reasons: maybe you want to use the highlighting feature of the Google Cache, maybe you want to send your query in Google referrals or you want to load search results pages a little bit faster.
"Google quietly made a change aimed at encrypting all search activity — except for clicks on ads. Google says this has been done to provide 'extra protection' for searchers, and the company may be aiming to block NSA spying activity," informs Search Engine Land.