Recently your CEO admitted clicking on AdWords ads "all the time" to test that everything is working (yes, I know ads clicked on from Google.com IP addresses are not counted) but, of course, AdSense publishers are not afforded those same rights. Granted, you provide an AdSense Preview Tool (but I'm on a Mac so I can't use it), and instructions on how to find the URL, but they are both too hard. As an AdSense publisher, I want the ability to EASILY follow an ad that I see on my site: e.g. it's something I'm interested in, or it looks dodgy and I want to investigate it further. The way I imagine many publishers do it now is to make sure they are logged out of the AdSense system, clear their cookies, and then use a proxy to click and hope for the best. If they had to fire up the AdSense Preview Tool, there's no guarantee they'd see that same ad again within the Tool.
I think you can guess what's coming... my suggestion is that you provide an easy way for AdSense publishers to click on ads on their site without risk of being thrown out of the AdSense program.
How about having a setting in the AdSense admin where you can specify your own IP address and not counting clicks from that IP address? Or not count the clicks when the publisher is logged in to their Google account? Or having a unique identifier on each Google Toolbar installaion and then allow an AdSense publisher to associate their installed Google Toolbar with their AdSense account so it identifies them and ignores their clicks?
On top of that, it would be fantastic if you would provide a one-click way of adding a competing ad to my competitive filter. Since you would know that I'm the publisher and not to count my clicks.