You might think it too fine a point, but I think any blogging product requires the ability to edit what one has written. To me, editing is a fundamental difference between blogging and social networks because blogging is about permanence where as the social network timeline/newsfeed is a black hole.

To me, what makes micro blogging different from social networks like Twitter is the permance I describe above, and therefore editing should be a fundamental requirement for all micro blogging apps.