I think this is a better idea than relying on advertising, but do you think there'd be enough demand for a white label version for it to be the core of their model?
Another approach: Fred Wilson's post today on comments constituting blog posts suggests that maybe they're building towards a sort of blogging platform for non-bloggers, where the aggregate of a user's comments on other blogs would form a new low-maintenance blog (on the Disqus site).