I, too, have the tiny holes bottom center on my most delicate jersey shirts. I thought it was my seatbelt, but i don't drive very often. My husband has them too, on some of his white tee shirts in the same place. I'm so glad we are not alone!
My latest theory is that they are caused by a combination of two or three things, based on what I've read here:
1. Cheap, poor quality imported cloth that has been treated with chemicals
2. Some sort of chaffing object like a seat-belt, or in my case the long strap of my bags that I like to wear across my front. Possibly even the dials on the stove that hit this spot.
3. Acidic alloys in the metal from jeans buttons, belts, and the buckles on my bags.
This never used to happen so it must be caused by the increasingly poor quality of cloth. I have noticed it particularly in tissue cotton and cotton-modal blends from gap, J. Crew, and velvet, which are made to feel thinner and lighte than normal. It has not happened to any of the cotton jersey tee shirts made by Uniqlo that I own, and I have had those for over three years. They are thicker and probably not treated with chemicals.
Thanks for all of your comments, they have made me feel less alone and less crazy! I hope my suggestions are helpful for others.