Adsense channels

Adsense can be confusing. I'm currently confused by channels and how to organize and use and interpret them. Confusions....
1- Do all clicks have to be assigned to a channel? If so, where do the blogger automatically added ads (like the ones on this site) appear?
2- Is there a "trace" tool to figure out where you have placed channels once my own records get screwed up?
3 - Is there some code in each ad (or inside adsense) that allows me to see which custom channel it is assigned to?

When you put adsense on your site, the revenue comes from three types of ads:
- adblocks
- adlinks
- search
The data on adblocks and adlinks can be viewed together or separately. The data on search is apart.

Channels - The channels are used to track the source of adsense revenue. There are two types of channels:

URL Channels - which are set up from within Adsense. You can use URL channels to track individual pages, or to track groups of pages based on the directory structure of your site. You don't have to change the code on your pages. Just login to adsense, Click the Channels link below the AdSense Setup tab, Choose the AdSense for content sub-tab, Click Add new URL channel, and in the resulting text box, and then enter the URL that you would like to track. The URL can be set to follow an entire domain, a subdomain, a folder, or any group of dynamically generated pages that you can write a rule for. Googles channel info.

Custom channels allow you to track the performance of specific ad units. By pasting channel-specific ad code into your pages, you can track a variety of metrics across a range of URLs. Use custom channels to track the performance of different ad formats, for example, or to compare different page topics to one another. To learn how to create and assign custom channels, please read How do I create custom channels? You can also turn any custom channel into an ad placement on which advertisers can choose to place their ads.

Note that since a single adblock can be counted in multiple channels (custom or URL). (Can an ad block be counted in two different custom channels?), the sum of individual set of stats might double count some clicks and revenue.