netmeg - 6:20 pm on Nov 11, 2012 (gmt 0)
My earnings vary *wildly* specially this time of year, so I don't think there's any set amount by Google on how much they're going to pay out.
Traffic quality is more than just where it's from and how they get there. It's also a question of who it is.
A friend of mine with a game forum really started seeing his earnings tank when his forum started attracting a much younger crowd. Google (and the advertisers) probably don't think those users are as likely to convert.