http://abcnews.go.com/GMA/Consumer/story?id=5177409
http://www.reddit.com/r/AskReddit/comments/18ekqf/as_a_canad...
http://www.quora.com/Do-real-Americans-wear-shoes-indoors-as...
https://answers.yahoo.com/question/index?qid=20101011193926A...
http://abcnews.go.com/GMA/Consumer/story?id=5177409
http://www.reddit.com/r/AskReddit/comments/18ekqf/as_a_canad...
http://www.quora.com/Do-real-Americans-wear-shoes-indoors-as...
https://answers.yahoo.com/question/index?qid=20101011193926A...
Interesting point: You also never see people on TV shows and movies taking their shoes off when they go to a house but I imagine this might be mainly due to the show not wanting to break up the action.
[0] http://en.m.wikipedia.org/wiki/Mister_Rogers%27_Neighborhood...
[1] http://photomatt7.wordpress.com/2011/10/07/mr-rogers-was-a-g...
During the rest of the year, it depends a little bit on the residence. I never cared if someone kept their shoes on in the junky apartments I lived in during college, but if it were my parent's well-kept house for example, I'd consider it rude to keep them on.
One of my friends has such high carpet and a close to the floor door that they can't have a rug immediately inside their unit. They contrived a mini parkour course to safely enter. You'd have to hop from the common hallway to a rug 2ft in and then to another one 2ft further, all in the name of etiquette and not wearing shoes "inside".