We had a bit of a pandemic with these little guys. 2 rode in on the back of some giant hairgrass we got from the lfs. We thought they were cute initially, even named them. Not a week later we discovered the gel egg sacs all over our tank. Probably 10 or 15 egg sacs in all. 2 months later we had removed nearly 70 snails. I still pull 2 or 3 out of the tank about every time I stop by, although the addition of ghostshrimp and a big ol' golden apple snail made a huge impact on how well they did. Our chemicals have always stayed pretty balanced and feeding to a minimum, but it seems if they are left uncontested they multiply to fill the void.
Sounds like, as long as you keep some competition in the tank, they stay under control. If you don't want them, though, get rid of them while you can still count them on one hand : )