Something very strange is going on in WordPress.com right now: people report entire blogs of messages gone missing, stats pages broken, categories messed up, all sorts of weird behaviour that could perhaps best be captured by the expression: “this service is broken”. Several of my blogs (some of them related to my teaching) are hosted in WordPress.com, so lets keep our fingers crossed. One of the discussion threads runs here (hopefully, if the forum area does not broke down, too): http://en.forums.wordpress.com/topic.php?id=17723&page&replies=6
frans goes blog 
Ok, it appears they fixed it really quickly. Still, having the entire service going haywire like this is really scary. Makes you consider backups rather seriously..