Out of my reductionist tendencies, I would say - can this question be reduced to "Can one post to a blog without opening an application?"

If one would like to not open an application (browser) to be able to blog what would make them like opening another application to be able to blog without opening the browser?

Unless that alternative application can bring more user friendly utility than blogging directly through the browser.

I am a web technology neophyte, so wouldnt' know if such a thing exists, but if there is ONE application (could be desktop a la Ipad or web based) that can simultaneously post on facebook, twitter, techcrunch, posterous, myspace, orkut, etc I think it would save a lot of effort to lots of people who like to post on multiple blogs, etc. If you can save a lot of effort to a lot of people, you got a product with customers.

If it can have a selectability feature if one wants to post just on one of these social/blogging entities, still better.

Good luck.