MongoDB Now Supports Auto-sharding
If your big data NoSQL database doesn't auto-shard, you might want to switch to open source MongoDB which will auto-shard all day long.
The newest version, 1.6, added the ability to subdivide and distribute a very large data set across many servers - auto-sharding. It allows data sets to scale horizontally.
MongoDB is used by Foursquare to handle its more than 100 million check-ins as users attempt to become the "mayor" of local bars and restaurants.