Robb makes the case that weblogs will (and do) scale more effectively than discussion groups:
Too much input is exactly the reason that discussion groups can’t scale. A serial thread on a topic with a million contributors swamps a discussion. As a reader, I can’t find the good posts in massive discussion group or mailing list. The signal-to-noise ratio is much too low.
However, weblogs change the equation. Each contributor gets a space where they can express their ideas. Their contributions aren’t buried under the weight of the community’s contributions in their personal space. The central hub of a weblog community provides a way to find these personal spaces, with each personal space acting as a filter or proxy for thousands of other sources. As the community scales the number of potential connections balloons. It isn’t a broadcast system with one source of content, it is decentralized system with millions of sources. It is a marketplace for ideas and insight. By subscribing to a particular weblog, I am opting to transact with their idea flow without the noise of other voices.
(That’s not the half of it.)
Follow the link for the rest of the argument.