Is Not That PersistentHow long do your posts and comments live?
Is Not Suited For Long Term UseAs time goes on, it becomes more and more difficult to get to older posts. The only way to do that today is to keep clicking 'More' button and hope that the post will pop up. And God forbid you accidentally click on a wrong kind of a link, because if you use the 'back' button on the browser - well, guess what, back to square one.
Is Not IndexableWhatever you post, goes to the black hole of your readership. Litmus test: try to find any of your public posts using any search engine. This demotivator comes to mind vividly.
Is Not SearchableNow, *this* is a surprise, *the* search engine company being behind it. There is simply no way to search anything other than people on Google+.
Wonder if all of these are bugs or features.
UPDATE (2011/09/20): It seems that "not indexable" and "not searchable" complaints are now fixed.