From what I understand gluten intolerance (including Celiac disease) is not at all like allergies where even a small amount of cross contamination can be harmful (or even deadly). Gluten intolerance really needs a solid amount (which many foods provide) to trigger problems, and the worry is really the long-term damage that can be done.
So I think that the "gluten-free" labels on things that obviously would not have gluten in them (e.g.: bottled water) is absolutely about advertisement to people who have been trained to think that "gluten-free" is always a good thing.
So I think that the "gluten-free" labels on things that obviously would not have gluten in them (e.g.: bottled water) is absolutely about advertisement to people who have been trained to think that "gluten-free" is always a good thing.