Back in the day my clowns would bite me too. I got tired of it and changed the way I deal with them. These fish are smarter than many people give them credit for. They can learn and are trainable. I've had many clowns over the years. Right now I have 8 clowns. 4 perculas, 2 clarkii's, 1 very large maroon, and a saddle back. Some of these fish I've had for years. Probably more than a decade for the maroon, and I can pet her. None of these fish bite.
Clowns bite because they see us as a threat. The only way, I know of, to change this behavior is to convince them that we are not a threat. If they charge and we swoosh them away, or hit them with feeding tongs, we're just emphasizing the point that we are a threat. Like kids teasing a dog. We'll simply make matters worse.
It's much harder to change this behavior once it starts, than it is to prevent it in the first place.
All of my clowns have been hand fed. I make it a point to put my hands in their territory on a regular basis. I don't make any threatening moves towards them. They grow accustom to my hands being in the tank, and don't see me as a threat.
When I first put my hand in the tank, my clowns will come up to see if I have food. Occasionally, the maroon will nip my fingers as if she's looking for food. This doesn't hurt and is nothing like the aggressive territorial attacks that clowns are capable of. Once she realizes I don't have food, she allows me to go about my business as she goes back to her territory and hangs out.
At the beginning of this video, from back in 2008, you can see my maroon go to the surface as I put my hand in the tank. She nips my finger, I tell her I don't have any food, (as if she can understand English :wildone

then she goes right back to her cave. As I move the rock into her cave, she gets out of my way, and watches what I'm doing from close by. Then after I remove my hand, she comes to the front glass to watch me, hoping I'm getting her food. When she realizes she's not getting fed, she proceeds to clean out her cave. At no time is she aggressive towards me.
<iframe width="420" height="315" src="http://www.youtube.com/embed/9KMOcpoVrDc" frameborder="0" allowfullscreen></iframe>