Due to the difference of features in the existing blogging APIs, there are two driver classes: Services_Blogging_Driver and Services_Blogging_ExtendetDriver (which extends the first).
Drivers extending Services_Blogging_Driver do only support creating, saving and deleting posts. They are not able to list (or modify) existing posts.
Drivers extending from Services_Blogging_ExtendetDriver do have more features: Reading existing posts, get a list of recent posts, and getting a list of the titles of the recent posts.