Jungle thieves!!!!
First off, let me start by saying there's not enough gold and exp in the jungle for junglers. Secondly, there should be a penalty for people taking farm from a jungler; for instance a jungler is on a large creep (theoretically) his jungle item marks the jungle creep with a debuff, should some inconsiderate person walk by and last hit the jungler's creeps, that person will get negative gold let's say -100g per large creep and -50g per small creep which will go to the jungler directly.
Some might ask; what if the jungler is willingly giving a buff to someone, that's fine, the buff just cost that person -100g which goes right to the jungler that placed a debuff on the creep.
What if two junglers (opposite factions) were on the same creep, trying to steal from one another, they would be immune to this debuff. The same jungle item that places the debuff on the jungler's creeps will also make him immune from it's effects.