From: Noyb, anonymous-remailer@shell.portal.com
So, lets look at the cost of ataining anonymity. For U people to communicate M bits (total -- 2 people each sending 2 bits is M==4) s/r anonymously takes O(U*M) bits multicast bandwidth for Chaum's DC protocol, but the repool protocol uses only O(h*M) bits narowcast bandwidth plus O(M) bits multicast bandwidth (Where h is the average number of remailer hops, expected to be a constant wrt U and M, smaller than U, and much smaller than M).
The repool could actually be somewhat worse than this. Wei has shown that if you don't send every tick then statistical information builds up surprisingly quickly to link senders and probable receivers, especially if there is a pair communicating frequently over a long period of time, arguably one of the main forms of usage of these nets. So everyone has to send all the time at the rate of the maximum per-user rate accepted by the remailers (say, one packet per tick). If this rate is considerably above the actual average communication rate of a given user then this will be much higher than O(h*M) (although granted it will not scale directly with U, increasing U will increase the desired packet rate that would satisfy, say, 90% of users). Hal