Perhaps instead of a 2/3 vote there can just be a minimum number of yes votes required. I don't really know what forum traffic is like, but if a suggested category gets 20, 50, 100 approvals, whatever the number may be, isn't that enough to suggest that it's wanted, rather than, as suggested above, people voting against a category because they don't like the person placing it. Of course if you want to hold veto power, you can use that in the face of several people voicing an objection to a particular suggestion. But the 2/3 approval (or even 50%+1) seems stiff, especially since it's typically the same people in the forums, and it's their biases the new submitter is up against. A standard minimum may make it more practical to get a new category published.