There is an interesting discussion on Unclutterer about whether or not people wear there shoes inside. Some people are more easy-going, but others take extreme stances on either side, for or against.
I think in this my opinion has been shaped mostly by my upbringing and by my exposure to Japanese culture. My mom kind of made us take off our shoes, but it was never a real serious rule. Grandma’s house, though, that is a place where shoes had to come off. There was a special entryway where you could take off shoes or boots in the winter time. Inside, the linoleum floors and soft carpets were always immaculate. You could just lay on the carpet if all of the chairs were taken by grownups, and the little kids always played on the carpet. This takes a lot of care and maintenance by my grandma, but it made us always feel super-comfortable at her house.
Japanese people have special shoe related customs for every situation. People always take off their shoes when visiting others. They have special shoes you put on when you get to the hot springs resort, but you still have to take these shoes off when you enter your room or eat dinner. There are still other shoes you put on when you enter the bathroom. When you use the scanning electron microscope you actually have to wear a suit with special shoes, though I think they do this in the US sometimes, too.
Come to think of it, my time in Japan has made me more sensitive to cultural differences. By this I mean that I am better able to detect when someone is doing something differently because of their culture and not because they don’t know how to do it the “right” way. I also acknowledge that some times there are two ways of doing something that have about equal merit, but which arbitrarily can be different in different cultures. This sounds really basic, but some people from my culture refuse to acknowledge this.
If it’s a tile floor, I don’t care about leaving shoes on that much. Tile feels dirty to me no matter what. But someday I’ll have a real house with carpet, and in that home I won’t care about other cultures. It’s going to be shoe-less.