Tell that to any AdSense publisher who has increased revenue 20-30% by moving ads a few pixels left or right, or by swapping the link color from one shade of blue to another. There are plenty. And Google is the ultimate AdSense publisher :)

There are plenty? Please cite sources. 20-30% improvements sound too good to be true for such minor alterations.

It's pretty much universal with AdSense. If you know anyone who makes a significant amount of money, ask them about it. Or just browse the AdSense board on WebmasterWorld.

I have personally increased revenue by over 100% by making small color and positioning changes, and this is also fairly common (I cited 20-30% because I wanted to be super-conservative in my claim).

But here are some examples:

From Google's official blog: Removing a border from an ad doubled revenue to $650/day:

http://adsense.blogspot.com/2006/05/unobtrusive-ads-can-boos...

Palette swap doubled clickthrough: http://www.cyberindian.com/web-marketing/article.php?article...

Webmasterworld thread: Most people did not disclose percentage, but some did (85% increase, 100% increase, etc)..

http://www.webmasterworld.com/forum89/14556.htm

There are endless examples.. just Google it.

The HotOrNot talk at CodeCon cited improvements of much more than that for a slightly more drastic change: moving the banner image to between the person's face and the rating bar, instead of above the rating bar. Unfortunately I don't remember the amount of the difference.