Up until now, my two nerite snails (one zebra and one red spot) haven't laid any eggs in the tank, and I was hoping it might stay that way. But sure enough, during yesterday's water change I noticed a few tiny white spots on the glass... nerite eggs! Oh well. They are a little tough to scrub off, but they do come off. If you have an acrylic tank though, forget it! The scratches you'd inflict on the acrylic surface while trying to scrub these eggs off would not be pretty.
Here's a photo showing the relative size of the eggs.
In this photo you can see some snaily bite-mark tracks leading up to the egg.
The guilty parties!