Decentralized directories sound fine, but they make the Gnutella network less anonymous and offer spyware servents an easy possibility to build an index of most shared files in the network. This is clearly not desired.

The nice thing in the current implementations of the query routing proposal (QRP), which is used between ultrapeers and leaf nodes, is the fact, that the QRP tables in an ultrapeer only contain hashed values of search keywords as a bitmap, which means that the ultrapeer knows which leaf nodes to forward a query to, but it doesn't really know anything about the files a leaf node shares. It does only know about some files when query responses are returned from the leaf node, but that still normally is only a fraction of the files a leaf node has to offer and that makes it nearly impossible for an ultrapeer to build an index of the files a leaf node has.