The maximum number of active Reporting Categories is 50 on YPN. Google calls them channels I think. I asked YPN for more. Maybe others can ask too. If you have 3 or more websites, the 50 does not go very far.
I have already sent in a recommendation to YPN that they need more than 50 of everything. URLs, Ad Categories, Ad Blocks. To fine tune your site you have to use a lot of them. I think 500 is a much better number.
I have been requesting more channels from the beginning. I have asked about 5 times. Google offers 200. If only YPN would offer 100, I would be happy. YPN is losing out with the meager channel offering. Few will test more pages without FEEDBACK DATA! I won't bother without per page performance reporting. I wonder how many YPN publishers are running ads on exactly 50 pages, like me. It's hard enough managing ads, but without channel data, no way.