At any rate, here's a quick and simple solution to disabling tabs in a tab container:
dojo.forEach(dijit.byId("myTabContainer").tablist.getChildren(), dojo.hitch(this, function(item, index, array) {
dojo.attr(item, "disabled", true);
item.onClick = function() {};
}));
Unfortunately, there doesn't seem to be a simple way to re-enable these clicks. Also, it'd be really sweet if you could simply hide some of the tabs in a tab container, but it sounds like you can only add/remove them.