There is a DigitalPoint Forums thread that has a poll asking members how many channels they use in total within their Google AdSense accounts.
Channels are basically a way to differentiate your ads within your account by site, by page, by theme, or whatever you want to differentiate by. It allows you to better understand which of your ads are performing well and which are not.
It is a bit sad to see the current results after a day. There are only seven replies. I would love to see others take the poll. Currently, it is hard to judge how many channels publishers use on average based on only seven responses. So let's get people to vote.
Take the poll at DigitalPoint Forums.