For CloudScale, as noted by CEO and founder Bill McColl, "Today is the age of big data," and "Data is growing exponentially everywhere. Excel is the world's No. 1 tool for processing and analyzing data, with hundreds of millions of users. But for big data, Excel is nowhere near enough." CloudScals service (Cloudcel) allows users to build applications to a large (billions) number of rows of data.
For FathomDB, their offering aligns more with providing database-as-a-service. Running on the Rackspace and Amazon EC2 cloud computing platforms MySQL databases can be had for a pricesolving the notion that SQL doesnt scale and providing database at much lower cost than say Oracle. Clearly the advantage here is FathomDB will managed, monitor, backup, tune, etc. a standard databaseeliminating the need for users to learn a different database system.