Massive Page Impressions

My main blog has Google AdSense on it. So I check in daily to see how many clicks and dollars I have made for the day. While I am there, I also check the page impressions for my blog. Something strange is going on today. The page impression count is up 16 times the normal amount. And the day is not even over yet. If this were normal traffic I would be excited, since on average I would also get a lot more clicks and cash. However I don't have a corresponding increase in clicks on my blog.

What could be causing this unusually high impression count? I figure it could be Google crawling my site. But Google Toolbar says my pages were cached a couple days ago. I would not think that Google would be back again that soon. I could be wrong. Or maybe it is Yahoo or MSN crawling the site. I think I did submit my URL to all three of these. Could it be some rogue search engine like My mind is racing with different theories.

In the big scheme of things, this is not really all that important. It is only interesting. The real goal of the blog and the associated Search Engine Optimization is profit. I am hoping that, regardless of page impressions, my click through rate (and therefore profit) shall continue to increase.