Scurramunga - 8:30 am on Dec 30, 2010 (gmt 0)

If it were ad blockers, wouldn't your impressions be way down too, not just CTR?

Yes you are probably right, but I am not 100% sure

I think it's a mix of ever more restricting methods that Google use to count real clicks and Adsense being on every crappy sites out there, leading to ad blindness.

Quite plausible. About three years or so ago when the decline first began there was a sudden ctr drop and I remember at the time discussing it here and in other threads:[url]
[webmasterworld.com...]

At the time it was obvious that such a change was not due to ad blindness or blockers as it was a swift and sudden ctr drop. However even since this sudden drop in 2007 I have seen further gradual decline. It is this gradual decline which has me thinking more and more about ad blockers.