In a generous move by Google, the Adsense team has offered to help optimize Adsense ads for some webmaster sites. The Adsense team has sent out some invitations this past week to some people for improving their ads performance. The response has been very positive and one member on WMW has commented:
They gave me great site-specific suggestions about ad placement. Implementation of their suggestions increased revenue. I also learned some new things about advertising. My experience has been that they are genuinely concerned about helping you increase income (theirs increases too, of course) in a way that also enhances a site visitors experience.
More discussion at Webmaster World - Adsense Invitation