[rjbwork]

I agree. I think there's a big hump in the middle of people who are like "hmm, this is relevant to me, i'll click it", then 2 long tails of people who click a LOT and people who click rarely or not at all.

On the other hand, there is a not-insignificant number of bot networks and shady clickfarm sites out there. Though, you can usually avoid being taken in by them by not being a cheapskate - quality traffic is more expensive. If you're bidding <$1 CPM for most things, enjoy funding a click farm.