Understanding Private Browsing
blog.mozilla.com
blog.mozilla.com
In the context of this discussion, percentage of Private Browsing activations would be more useful.
That said, there is not generally a spike in usage at lunch for anything else. For many other metrics of interest we see a familiar sinusoidal wave of usage, with the low point at around 3 or 4am, and a high point at approximately 6-7pm.
Thus the spike in usage at lunch turns out to be quite unexpected.
http://www.usenix.org/events/sec10/tech/full_papers/Aggarwal...