depends on how you look at it , they will in fact grow over alot of stuff, a friend of mine back home has them overgrowing his clam and tank.
they can be intrusive but they wont harm your corals by stinging, they over grow the less aggressive ones though
brown is ugly anyways so i would get rid of them if they were in my tank which they are and which i am lol
just dont complain about numb hands or tingly fingers....could start a debate
pppp