Robert_Charlton - 10:27 am on Feb 11, 2013 (gmt 0)
besnette - Yes, this is one of the most annoying types of sites to encounter... probably tricky to detect algorithmically... and yes, I've had the same thought you've had that they might be faking engagement.
I think they dropped for a while after the first Panda and above-the-fold roll-outs, as they were greedy about AdSense as well... but recently I've seen them come back.
The sites probably calibrated the ad threshold level enough that the above-the-fold algo is no longer hitting them as much. Probably a combination of signals is involved, and it may take some trial and error for Google to get rid of them. AI using heuristics requires trial and error.
I keep thinking that Google does not want to cut too deeply all at once, as that's more likely to produce collateral damage.