johnhh - 11:17 pm on Jan 12, 2012 (gmt 0)
not always, we had a spike in traffic a few months ago, it was related to a popular news item that referenced a particular [widget]. It just happened that we were one of only a few sites that had a page on this [widget].
Google is giving the site a test to see if their users respond well to it
Suggest the OP also looks at the time of the day for his traffic increase/decrease.