The news coming out of WordCamp SF is that WordPress.org and WordPress MU will be merged, albeit at an undefined point in the future.
I know at least one person who will want to point out that Habari already has single and multiple blog support in the one package.
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[...] over at WP Fun also pointed out that Habari already has this feature built in. I believe Movable Type also has a similar multiple blog features as [...]