I'm not sure if this has been covered or not in previous posts by other people, but drafts are now searchable and entirely viewable in google, and can be seen on your user page if you recommend them (if you're the sort of person who recommends their own posts).
I don't know about you, but I've used the drafts function as my own little private archive to keep posts that I didn't want to be public any more, but didn't quite want to delete. My own truly private blog, if you will. People still can't go to the draft itself, but the subject and first few lines of each draft can be found in public Google searches.
ETA: as per Halfeclipse's investigation (see comments), drafts are entirely available through Google. So, if you've been working on a big coming out post but don't want it public, you'd better choose a new medium.