Updating a self-hosted CMS sometimes is a scary thing and many people don't update or update very late. We all know how bad this can be. With Bear CMS your management tools (we don't call them backend because we offer live editing) are always up-to-date because they run on our servers. You get full control of your website (write custom PHP code for example) but don't worry about securing and maintaining your DB and administrator tools.
The closest thing I've seen to this is the platforms aimed mostly at providing providing datastores for sites/apps that pull in all their dynamic content on the client side. But these have the obvious advantage to the content manager of the client side app potentially being a static page pulling in content via js or a mobile app, as opposed to an Apache server with a PHP installation that still needs patching and securing...
