Clay Shirky addresses the issues of scale in two-way media:
Prior to the internet, the outbound quality of mass media could be ascribed to technical limits — TV had a one-way relationship to its audience because TV was a one-way medium. The growth of two-way media, however, shows that the audience pattern re-establishes itself in one way or another — large mailing lists become read-only, online communities (eg. LambdaMOO, WELL, ECHO) eventually see their members agitate to stem the tide of newcomers, users of sites like slashdot see fewer of their posts accepted.