Yep, this is another anti-exploit situation. I remember back in WoW Beta it was possible to get the exact range to a target. Unfortunately people were using that to stay just outside of their opponents range while using their max range weapon/spell.
Someone actually put together a mod that looked at your target, then based on their class/level decided what their maximum range was. Then you got a colored indicator - Red you are in range, green you are out of their range and safe.
Think of the possibilities in PvP
