nomis5 - 5:07 pm on Jul 22, 2012 (gmt 0)
According to the mobile optimisation talk I had with a G rep the 300x250 format is by far and away the biggest earner. That matches exactly what I see on my mobile site.
The problem is that putting that ad format above the fold occuoies a lot of mobile space and looks a bit cheap. So I have a 300x50 ATF and then a 300x250 further down. Even so, the 300x250 outstrips the other ad fomat by miles as far as earnings are concerned.