Background about MyKolab.com
MyKolab.com is a special service that provides you with an in-built escape hatch through the Kolab Groupware Server technology which you can choose to self-host at any time. So should this service be discontinued or no longer be what you want, you can move, freely, with all features and all data. No lock-in on any level, and the health of the solution and further development of that escape hatch is supported through the MyKolab.com service itself.
Read more in the background story by Kolab Systems CEO Georg Greve: Building the Open Source Cloud service that was missing.
Update 16.8.2013: Opensource.com is now featuring "Do cloud right: Four critical steps to selecting the provider for you" as a checklist of the primary principles applied to MyKolab.com when selecting your cloud provider.