I too have read this kind of discussion before, and it is funny how exercised people get about it. I don't ask other people to take off their shoes, but I do have acquaintances who do - I'd prefer not to sit around someone else's house in just my socks or bare feet, it just feels weirdly and inappropriately informal (and you worry about whether your socks have holes or silly things on them, or your toenails need to be trimmed), but I will do it of course if people ask.
I don't think the Canadian tendency to no-shoes is just about the weather; it's cultural too. I grew up in the (American) midwest, and we had plenty of snow and I didn't know anybody who asked guests to take their shoes off. Knock off all the snow in the winter, sure, or remove your snow boots and wear regular shoes, but that's it.
I personally have an issue with not wearing shoes in the house as far as foot health goes - I used to do it all the time, and it's made my feet problems worse. If you're just sitting, it's fine, but if you're cooking or doing real work, the support of shoes is helpful. That's why I wear them in my house, most of the time, even though I love the feel of being barefoot.