They can be a problem with various corals/animals. More commonly "duster" type corals and zoo's. They are also guilty by association when found near dead/dieing corals. Keep in mind these guys are opportunistic feeders but they should not be immediately blamed unless caught red handed. Even then, look for underlying causes. As for the GPS, it is possible as the polyp size is in their realm of goodies but that said, the circumstances of the tank are an unknown and it's quite possible they where not properly fed. Also be sure the person you read about did not mis ID
the shrimp as a camel back which can often be the case.