Chopping etiquette

[ChuckyB]

Playing a 4/8 kill game in Calgary last week.

A pretty loose game was undergoing a spell of tightness. It was folded to me in the SB. I had 66. A couple people at the table (neither me nor the BB) said "chop?" I was ready to raise, but I started to suggest to BB that I call, and we run it for the hell of it.

Before I could finish, BB mucked his hand (assuming there was going be a chop). The dealer (shooting me a disapproving look) ruled that since BB mucked, I was the winner and there would be no chop. (Woo hoo! $6!!!)

I'd never run into a chopping situation before.
Am I obliged to chop, if it has been happening around the table so far?
Is it customary? Does that change at different limits?
If I do it once, do I have to/should I do it every time during a single session?
If I've got a good hand why would I want to chop (besides maintaining goodwill and loose play)?

Please help.