Had not thought of that. I may need to give that a bit of thought and inquire how the few I have sold have fared. I have taken steps against some pests for that exact reason. Obviously any real distructive pest is elliminated and some just because of the reputation. Not as big a question as you might think as the clams I bought came from the very reputable sources, likely some of the same as yours and the snails were common. I have never carried clams as a specialty, if I ever go that route this would be a factor. It would not be hard keep clams cleaner than the larger distributors. There task is overwhelming given the volume of clams they move. These things obviously exist in the mariculture systems. That would further support my earlier premise.
GB WI, we have likely meet at reef events. As many frags as have sold in WI you may even have a coral or two whose mother colony is in my system. I have LPS colonies that are on four and fifth generartion frags and sps were I have lost count. I don't name my stuff, maybe i should but just seems so silly, most likely costs me some, when one of my LPS sells on RC it would be good marketing if it had a brand. If i get much deeper into this, still a hobby, out of control some, but still a hobby, i may turn to the dark side with branding corals.
- mark
Funny, I did the same thing with the pinched mantle. I saw it for the first time a few years back after adding a new clam. I left the clams alone, did a few water changes to make sure they would have every chance to fight it off. It slowly went away. I have a lot of diversity of in my tanks. It is hard for any one organism to explode when there are so many to compete with. I think 19 out of 20 of the maligned critters in here are harmless in a well balanced tank. These clams live forever in the wild and they have the full spectrum of critters to deal with. In a bare bottom tank where the owner is afraid of anything that moves, poison when they see a flat worm, boiling rock to kill hydroids, on and on, any potential pest has a heyday when introduced to a tank like this. I see these little snails occasionally seldom more than one and I leave them alone. I hate to admit how long I have been keeping clams. I have always seen a few of these associated with the clams. I plan to one day soon start a post where i discuss the set up for my main tank, If a newb came into the beginners forum and suggested a tank like mine they would tear him to pieces. Many techniques from the past have for no good reason fallen out of fashion. The techniques that have replaced them have shortcomings, much of the complex equipment and more troublesome problems are the result of abandoning the principles that were proven years back. Bacteria and micro fauna are your friend. I do see a few prominent reefers who use techniques similar to mine. I hope these schools of thought are rediscovered soon. It is a lot cheaper than calcium reactors, nitrate and phosphate filters, ozone, or whatever electronic bell and whistle comes along next. Don't misunderstand I am in favor anything that works, but prefer more eloquent natural systems to the tail chasing that these overly complex and expensive systems employ. 
