Warning: bathroom talk follows.
Maybe it is some guilt trip put on my during my potty training years, but I hate for people to know that I am going number 2. Number 1 is okay, but number 2 is not to be mentioned. When I was in school it was the worst feeling knowing that you were going to be gone long enough that everyone would know that you were in the bathroom stinking the place up.
Rationally, I know that everyone does it and that it is natural and nothing to be ashamed of. This does not stop my anxiety. If I am in public I will wait till other people are out of the bathroom before I exit the stall. I will use bathrooms in less public areas for fear that someone may see me go in and then see me come out quite a bit later. Then they would know. My anxiety about public bathrooms was increased in the 1980's with the "get AIDS from a toilet seat" urban legend. Add that to the state in which people leave public bathrooms and I would almost rather chance holding it than go in public. I judge restaurants, not by their food, but by how clean they keep their restrooms. I try not to go at friends houses. I not only feel that they know by how long I am gone but they feel disrespected that I do this in their house.
The worst part is when someone you know follows you in. Do you fake only having to go number 1 and come back later? Do you allow them to see your dirty little secret. The other day a co-worker followed me in and I hit the stall. The guy sees me and starts up a conversation. This is wrong on multiple levels. First, it breaks the rules. Second, he knows I am here and will here any noise that I make (can you try and go quietly? yes. . . yes you can). Third, by talking to me others may be alerted as to who is occupying stall number 3.
Strangely my body has compensated for this in some way. I can make it in and out so quick that people think it was only a number 1. I am unsure if this is a reaction or if I just eat enough fiber. Cell phones are the exception to me making any noise. If you are on a cell phone in a public bathroom, I will try my hardest to let the person on the otherside of the line know it.