What the f*** has happened with Adsense clicks over the past week?

I usually have no problem in generating enough clicks to make the minimum S100 income every month – usually by the middle of the month.  So far in December my Adsense earnings are less than one third of the amount for the same period in November. And, compared to last December, the rates are pitiful.  Page eCPM is down: the only thing that is not down is my site traffic, so that is not the reason for this massive fall.  At least I have other sources of income, and good job – if I was relying on Google for my Christmas spending money, it would be a bleak celebration around here.

I am not alone – this problem is affecting thousands of Adsense publishers, this thread on Webmaster World shows the misery is being shared around the world at present.