Bumping someone whilst on fire should set the bumpee on fire.

[atomic1fire]

Having played enough hippie rounds to know sort of how the whole fire thing works.

I think being set on fire by other dudes that are on fire just encourages you to avoid people on fire, and spray them with the extinguisher only when convenient.

I could see it working for a chemical like napalm, where that stuff sticks to you. Or when you're so engulfed in fire that it's obvious.

On the bright side it would encourage people to build more flamethrowers and and pipe bombs probably.