Let me just put this all to rest. I'm a developer for SME Server. I am also the one running the contribs.org website servers. It isn't a single server but a cluster of about 28 virtual machines running on top of 7 physical machines. These machines handle wiki, forums, mailing lists, bug tracker, build system, master mirror, mirror tracking, and a lot more supporting functions that go on behind the scenes.
I'm also a developer for ClearOS Enterprise. When it didn't look like CentOS would be able to put out 6.x in a reasonable amount of time I took on the task of rebuilding RedHat sources myself. I am the one one that started this project and am the only one building ClearOS Core at the moment. My rebuild was called ClearOS Core because I was sponsored by ClearFoundation to build it for their next release. Not much has been published yet but it is an internal stable build of upstream sources and lags by about 2-3 hours.
I personally do run SME Server. It is a great distribution and is plenty stable and secure. It just isn't up to the task of running a cluster. My cluster is built with CentOS 5.x on the physical machines running RHCS. On top of this is a mix of ClearOS Core and RHEL6 boxes. I'm able to build a VM with 6.x that is much smaller and lighter than SME every would be and that VM can be dedicated to the functions that they need to run. This makes it easy to put it where it needs to be in order to balance the load. It also makes it easy to rebuild if anything happens to that VM. This way if something gets hacked (hasn't happened yet), I just need to take that single function offline and rebuild it.