A month ago there was a bug with the Facebook Like button. It was reported to have an impact on some user's analytics packages but I didn't hear much from AdSense publishers on this topic.
A WebmasterWorld thread has one publisher claiming he saw a huge spike in AdSense income when the bug was happening and then a huge decline in that earnings once the bug was fixed.
He shared a chart showing the traffic just from the Facebook Like button:
The Google AdSense publisher explained:
On April 10th, my Adsense earnings went to the roof. I couldn't tell the reason for that, but I decided to be glad and do not bother about it.
Much to my surprise, my earnings kept going up over the last days (with a quick weird drop on the 16th), until they came back to the regular levels on April 20th.
The only unusual thing that I could find was an amazing raise on the number of times the page "?fb_xd_fragment=" was opened on that golden period. For those who don't know, that's an URL that shows due to a bug on the Facebook Like button, which doesn't support some browsers.
The rest of the site's traffic was exact the same, so why the Facebook Like button error started showing up A LOT more often on the logs? And even weirder, why did it impact on the Adsense earnings?
Of course with huge surges in traffic and unusual spikes, you need to be considered with Google investigating the reason for the surge - it can ultimately lead to your site being banned from using Google AdSense.
Did you notice a change due to a bug like this in this date range?
Forum discussion at WebmasterWorld.