It's broken in the larger sense that Eric mentioned: costs are not incurred by posters. [...] Very long term, when message costs are borne by the sender, this problem goes away.
I really doubt the problem goes away. Message costs have some restrictive effect, but they are not a panacea. (They are a panacea for supporting remailer services, but that should be obvious.) Transmission costs are dropping so fast that it is conceivable that the cost of a broadcast of a three page message to everyone in the world will be less than a dollar. Mailbombing might be solved by message costs, and will be a deterrent, but mailbombing is such a blunt weapon. As I recently argued, the problem is not individual disrupters but salience in general. Usenet is broken because it transmits everything which is sent to it, without any sort of judgement as to the propriety of the message to the newsgroups to which it is posted. Paying for the message does not solve the problem of newbie questions, or flame wars (low bandwidth data, high bandwidth emotion; flames are extremely compressible), or digressions. Eric