Frenzied Berserkers are a challenge to play, and a reflection of the player in game!
I've played an Goliath FBR for about a year in Eberron, and am playing one in the city of the spider queen now - it was/is a great character, added much to the group and the group helped him a lot to deal with the loss of control he sometimes experienced.
Some want to see the FBR as a PvP Team-kill monster. He's not. A frenzied berserker is a barbarian that looses control. Like the "Hulk Smash" or Dr. Yekyll/ Mr. Hyde - a frenzied berserker must come to grips with his psychotic nature. This lead my character to be very lonely, never allowing anyone within 5' (or within arms reach, in-game), never waiting for his friends to stand by his side and maniacally throw himself at any opponent - afraid to be caught where the thing could happen again (background: he woke up with several of his friends (and a rather sizable party of drow) dead by his own weapon - the rest of his tribe had abandoned him (rightfully he felt), and he adventured searching for ways to regain control (Righteous Wrath would've worked, game ended before my next feat selection).
The Drawback can be viewed as a RAW excuse to PvP/TPK - but only to those inklined to think along the straight and narrow. It is to my mind a powerful way to force any group to evaluate whether they think the player is worthy of such power. With great power comes great responsibility.
On the possibility of all planets lining up and an unintentional PvP occurring (they must of course be unintentional - anything else is evil and no fun) - how is that different from an Wizard misfiring any spell, a rogue overlooking a trap. Excrement happens, the point is to try your stinking best to avoid it.
Remember the FBR has no choice in attacking his friends after he fails his will save) something you must try, IMHO. It is not something he wants to do, neither does the (non evil) rogue step over a trap or a (non-evil) wizard intentionally misdirect his fireball to include his allies. It is something HE must live with. In my world, I try to help my friends with their troubles. Granted, none of them a psychotic murderous freaks - bu I don;t spend many out-of-game hours taking 20 on search checks for loot/secret doors. DnD characters lead a different - much more violent life. A well played frenzied berserker is a great addition to any game.
