About 5k.
You are smart enough to understand that having a team full of low geared people is frustrating right ? If you are, then you understand how bad your post is. If you die in one hit, your place is not in a bg. A bg is a team work and if you can't help the team, don't join it.
If you are under 4k gs, even if you plan to do objectives you won't be able to. You can't defend a base, you can't carry a flag, you can't kill a flag carrier, etc so in response to what Natasmai said, no, a gearless person is not valuable. Plus, Natasmai compared 2 different things : zerg vs objectives. WRONG. Compare objective seeking lowbies with objective seeking geared people. Does a lowbie team stand a chance ? NO. Even in the case of a zerg, there's a high chance for you to lose the bg even if you follow objectives so again, gearless people have no value.
Just yesterday i saw a horde prot warrior getting attacked by 5 alliance lowbies in arathi at stables while he was defending. I didn't even bother to help him since he was just laughing at how they struggled to take a little hp off him. Such value, much usefull, very potential.