There are pros and cons.
There is a potential for injury (for example if your finger moves at the wrong moment) and bacteria transmission in hand-feeding. It might also cause the chameleon to associate your fingers with food, to the extent that it tries to bite or shoot your fingernails, etc.
On the other hand, it can help a positive association with you, rather than seeing you as a big frightening predator. It also gives some people a sense of connection to the animal, and/or a "cool" factor.
I personally rarely hand feed. I dont see sufficient benefit, and the animals eat fine without my fingers in there.