Much depends on how you want to use the belt. If it is to be a general-purpose flexible item, then indeed it should be rigged in multiple segments -- and for more easy in posing, look into rigging "EasyPose" dials into it. If it is to be fitted to a particular figure, then there are several rather different methods to do so. In that case, the only groups in the final object would be those needed to apply different materials. In my own opinion, rigging a belt as a conforming clothing is not the most convincing way to do it...the kinds of bends and deformations a conforming figure create are not those natural to an actual piece of leather or fabric. They work better when parented -- rigged as a smart prop, even -- but for extra realism there is a scheme that uses ERC to allow the belt to be parented to the hips but influenced by the abdomen.