I read a similar story not too long ago, that one was cut in half and over 6 foot.
I pulled such a worm from my rock about 2 years ago, it was only 6 inches but the same type. It is some kind of bristle worm that looks like a centipede to me. It ate my five headed frogspawn in a single night.
Never seen Steve Weasts website, I guess. This guy had one of these, in his personally owned 850gal tank.
I'd have nightmares, if one of these things popped out of my live rock.
Here's Steves "Worm Incident"... http://www.oregonreef.com/sub_worm.htm
EDIT: RSlinger beat me to it. lol I guess I took too long to post.
yup, seen steve's worm, but i got the feeling this worm was pretty big. but, of course, therer's nothing to scale how big the blue aquarium's worm is, just looksl ike a monster