I am fine with Jeff's rule, as I envision combat very abstractly, where each roll encompasses the cumulative result of various bits of dodging, darting, ducking, circling, feinting, etc among all combatants. Your archer might have his target perfectly picked out, then fire, only to discover a teammate has just stepped into his arrow's path at the last second. Whoops, you must have rolled a 1-3 on that d20! Now roll again to see if it did any damage.
Ex:
Bill: I fire into melee (rolls 2)
Ref: Uh oh, looks like a friendly fire incident. Roll again.
Bill: (rolls a 19)
Ref: Your arrow nicks Jim in the calf.
or
Bill: I fire into melee (rolls 2)
Ref: Uh oh, looks like a friendly fire incident. Roll again.
Bill: (rolls 7)
Ref: Your arrow bounces harmlessly off of Jim's greave (or snaps on impact, flies wild, etc).
I also think friendly fire rules are a nice check against the overpowering of bow specialization, so I always use them. YMMV.