They are very common, harmless ( other than cutting your fingers when moving rocks around) and nothing I know of that you would actually want to keep in your system eats them. You can try to break off the tubes as close to the rock as possible, or even epoxying over the end of the tube to kill the snail.. Most folks seem to just live with them.
i hate em too. they r harmless but unsightly. they dont get eaten cause the hard tube protects them. once u crack its tube, my cleaner shrimps goes right for them.