From what I've heard, this happend on SMP1, there was a thread about it but I don't know if it's still open or not and not sure if they fixed the problem there.
I have seen these i dont know how people have greifed these :s and please dont use all caps in the title in future
I have a feeling JustinGuy or a staff member is going to lock this thread and I am 200% sure JustinGuy is aware of this problem and that he is working on it asap, so please don't explode on the subject that could be very minor