From: lcottrell@popmail.ucsd.edu (Lance Cottrell)

Even if you are using a perfect network of remailers, you can still be tracked. Only so many messages pass through the network of remailers in any given day. If Alice sending a message usualy correlates with Bob receiving a message, it is likely that she is sending messages to him. This was discussed in some detail in several messages by Hal and Louis Cypher.

Actually I don't think I considered this aspect of the problem. Probably you are thinking of Wei Dai's posts along with LC's. Hal