@Andrew,
The question bloggers will always ask themselves is, "does this help me?"

If the blog network or central aggregator blog can make us richer, more popular, or more respected, then people might join. That's a hard sell for a site/network that currently doesn't even exist.

The proverbial stars would need to align in order for something like this to work. There are just too many egos to deal with, among other challenges.

However, if this were an official thing (say, hub.wordpress.org) and only the crem-della-crem were initially invited to have their sites officially aggregated, it might actually work. Sort of like wordpress.tv, but instead of videos, it would be a WordPress tutorials aggregator. Authors get to maintain their own blogs, and the community gets a central resource to find both good tutorials to read, and good tutorial writers to follow.

Pie in the Sky.