When I check my portage tree there are 33 packages available, but the online database only lists 27. Missing is bittorrent, cccp, freenet, kmldonkey, overnet, pysoulseek.
Sorry, I am talking about the net-p2p directory.
This is because the online package database only shows the latest stable version of package and if the package doesn't have a version marked stable yet, it's left out.
as Rainer said, this is expected behavior