no the point is , while its "api" is great , you cant replace your RDBMS with a mongodb , while other solutions like redis or couchdb are "minimalist" they are better suited for what nosql db are for , high availability and scalling.
Unfortunately that's not true: it depends directly on what you are doing with your RDBMS - there are many work loads which are better suited to MongoDB. Obviously there are also many which are not.
Unless I'm out of date, Redis and High Availability don't go together in the same sentence; awesome as it is, it's still a single point of failure.
