Mobile Bay Reef Keepers

I was identifying some hickhikers on a new piece of rock... found a limpet (I think). From what I can tell these guys shouldn't bother anything although I've heard rumors of them hurting zooanthids. Does anyone have any experience with these guys? Will they hurt anything?

BTW - Here's a good page about them if anybody's interested:
http://www.mesa.edu.au/friends/seashore ... erica.html

Liz's tank had several of those... they were harmless, and Charlie took them with him to louisanna for their new 240G.