Air pots are all about air circulation and drainage. Due to the large open gaps on the sidewalls and base of these containers air is able to percolate easily throughout the growing media contained within. This eradicates risk of root rot but it also produces a very vigorous root system, which is formed predominately with fine feeder roots rather than thicker storage roots which you so often find circling the inside of conventional containers. This effect is produced as the root tips reach the container wall and meet with air, they stop growing and new roots issue from the plant stem.
Bonsai: Many bonsai enthusiasts use colanders and air pots during the development phase of their trees. It is important that for you to be successful in this technique, that you use fast draining substrates, water and fertilize a lot.
Carnivorous plants: The most likely use for these air pots would be for Nepenthes. This carnivorous plant grows in nature on rocks or in the cleft of tree branches and other such well drained areas. To avoid the delicate roots of these plants rotting drainage is key. Air pots are a good alternative to more conventional closed wall containers and you could even hang these if you are prepared to make some minor modifications and attach some cord or wire.