One of the really interesting announcements in the Cloud space these days has been from VMware and Salesforce.com with their vmforce offering. Their claim is "The trusted cloud for enterprise Java developers". Correct. It is a cloud environment where Java developers can build apps with a Spring Eclipse-based IDE, where they can use Tomcat, and so on. Thus there is an environment do build and deploy Java apps in the cloud.
Beyond that, force.com functionality might be used. That is definitely interesting because force.com provides a lot of services around business analytics, reporting, mobile device support, and many other functional areas. That might speed up development significantly - sort of rapid development support in that environment.
However, the most important point from my perspective is that vmforce is much more open than force.com itself. The force.com platform is proprietary - and that equals to lock-in risks. Thus users have to analyze whether the advantages of rapid development, the force.com database, the force.com services and so on are worth the lock-in in the sense of very limited portability.
When choosing vmforce, developers can build Java apps in a standard environment. Thus, they can avoid these lock-in risks. If they opt to use force.com services, they have to pay a price in the sense of using specific services from a specific vendor. However, with a good software architecture the apps can be built in a way that allows replacement of force.com-specific features by other services.
With the combination of force.com and vmforce, Salesforce offers choice to developers - from a more closed, very rapid and efficient environment to a very open, but a little more complex environment plus the option to combine that in a flexible manner. That makes sense, from my perspective. And it is definitely worth to have a look at vmforce and to play around once they will provide their preview versions this fall. That is, by the way, a negative point: We are still some time away from production use of vmforce.