The Bonsai Framework concept of Cloud Density is the philosophy of reducing Cloud cost using a combination of container technology (isolation technology and techniques like using zero footprint and multiple instances.
Some examples of enabling isolation technology are Container (FreeBSD Jails, LXC, Docker, Garden) and /or 0F (Zero Footprint) to reduce the number of virtual machines on the platforms (Cloud Foundry, Apache Mesos).
In best practice, the output of Cloud Density should reduced cost due to less Cloud virtual machines. At the same time, the system should match the service level of a standard larger cloud.