This is cool for sure, but I fail to see the audience. Microblogging may work well enough, but for anything more substantial you will likely still need to make edits within their app down the line — even immediately after posting when your markup is inevitably rendered differently than you expected.

E-mail has an "open protocol / data ownership" appeal to it as well, but that's kind of a facade in this case; you just get to store a log of your API calls, essentially.