They also mention their goal, when SE was started, was to make the web a better place (and to get rid of Experts Exchange). A "ghost town" has little chance of making the web a better place. It kind of makes sense. However, if you run a private support site that requires login and is, therefore, not googlable, it wouldn't pollute the web and they could consider hosting it, provided their platform supports the feature.

If you want to have your own SE-like site, you may want to look into AskBot - it's very good.

OK, so are they worried ghost towns will reduce the value of the stack exchange brand? I mean, even if they are being altruistic, I still don't understand the societal harm caused by ghost towns.