In my home country (Sweden) it is considered utterly rude - it brings in the dirt, is unhygienic and causes extra work to the hostess! And most people have wooden floors (carpet was faced out in the sixties - unhygienic).
Here in NZ however, most people walk in with their shoes. And most people have carpet.
In our house we have wooden flooring and we take our shoes off, but most people who come over don't. I hate it. They see all our shoes by the door, and us wearing socks and they keep their shoes on? I don't like it, especially now, as I have a baby crawling around on the floor.
That said, several of my mama friends, who are a bit "alternative" as well (EC, homebirth, extended breastfeeding, cloth diapers, no/selective vax etc), don't wear shoes at home either.