Cone snails are pretty different than conch snails. Most cone snails have much more attractive patterns on them. It appears that the foot of the cone snail is much larger and wider. The eyes are shorter on the cone and the snout (mouth of the conch) appears to be the only appendage other than the eyes. There appears to be a snout and a mouth and eyes on the cone snail.
I think the stories that Adam have mentioned is when people have stepped on them in the sand without noticing. I've heard something similar but I agree with Adam on the rest of his statement. Although they may not ever harpoon you, its still a risk having them and with anything venomous, you should take precautions.