I start all my chameleons off in enclosures that are 2x2x6 and move them into 4x6x8 when they get older (I am currently building a new 4x6x8 for my diego suarez)
The argument for using a small enclosure is it does make it easier to monitor food intake for a young chameleon. However, this is irrelevant if you cup feed your chameleon (as the food stays in one place) or use feeders that don't run off and hide (I use locusts as my staple feeder and these things are happy to climb towards the basking light; where the cham will normally be). Also, if you take your time to feed a chameleon (which most people do) by putting the food in in the vicinity of the cham, they will pick it up prettyy quickly and go hunting!
My final though is always that a chameleon in the wild would have acres of space to explore and find food and they manage perfectly well on their own then, so why should being in captivity make any difference. They're natural born hunters afterall!