How can I disable a category The green bubble (status is enabled) next to the category items in the category overview suggests that you can disabled/enable the category. 

Is that possible? And if so, how?
I don't think you can disable categories with the current version of Craft. But you're right, it currently looks like that categories are prepared to get disabled.

Update:

Categories now have their own edit pages in Craft 2.3, where you can set the status. And you can even set it on a batch from the category index page!