Surfnvb7,
Good question. Zoanthids aren't used for much, definitely not food or anything. Different colonies and species have different toxicity (from what I have read), but no one really knows what colony or species has what, kinda scary...
The one field where you do occasionally find zoanthids being used is in chemical-related research, and big med companies. As a relatively under-investigated group of animals, in possession of some nasty palytoxin, they are a hot topic. Lots of patents waiting to be found. The good/bad news is most of these compounds, once identified, can be made synthetically, so most of these companies don't even know what species they are dealing with... that is my (and a few others) job I guess!
Also, one of these compounds (norzoanthimine - I think) has been shown to have anti-osteoporosis effects - I think this was in Science a couple years ago. Again, an unknown Zoanthus sp.
Does this help?