Ahh, Yes... the age old question to hug a bristle worm or not...
I have lots of tanks. In one tank (6 years running) I have pulled two bristle worms out of it. Six line wrasses are great for munching the little buggers. Back to it, my big tank Next to none. I perodically pull a piece of live rock out an throw it in a bucket of fresh water over night. any of the little buggers that are there usually crawl for their lives and die a horrible death. My main tank rarely see them.
My big eaters tank. Lots of them. Always pullin them out.
I think that it's like any thing good and bad. I don't belive that you will see a lot of them if your waste/organics are down, ie. not over feeding. The other side of the coin (big eater tank) lots of waste and organics sludge lots of bristle's.
I have one recorded event of a bristle worm eating a clam. Isaw him and could not get it out of the clam.
Fire worms and bobbit worms are way way worse.