well...I have those too, but they're really small and put out small strands of mucus. All of my vermetids look like the one pictured here on melev's site:
http://www.melevsreef.com/id/vermetid.html
From what I could see...the "thing" in my video didn't have a hard shell and had a glob of mucus rather than just a small strand. I did eventually find out that spaghetti worms use a hardened mixture of mucus and sand to form the inside of their burrows...so I'm wondering if that's what was going on?
When I woke up this morning that web was gone...hopefully it retracted and didn't just blow onto some coral :/
(sweet video in that link, btw Chad. Don't think I've seen them up close like that before)