I don't wear shoes at home apart from when getting dressed at the start of the day and then taking them off when I get back home. Having said that, I never object if others leave their shoes on (unless they're trailing large amounts of mud) but since I take mine off, most people notice and automatically remove theirs anyway without me having to say a word. It helps that I tend only to let considerate & pleasant people into my home in the first place who notice what a host is doing and out of politeness would automatically follow suit. When visiting others socially, I just follow the habit of the household, and don't much care either way.
On another note, if I'm making a house call professionally, I always leave my shoes on unless specifically requested to remove them. Leaving aside an issue of maintaining professional boundaries, I visit some less than salubrious houses occasionally, and believe me, you sometimes really want that extra layer of protection between your feet and the floor! Also, there's occasionally the need to make a rapid exit, so having shoes on helps... Having said all that, if I don't expect to need to be leaving in a hurry and the house is nice/clean, and I see the person answering the door is shoeless, I will ask on entering as it's a free way of breaking ice/building rapport/showing respect which can set off the consultation on the right foot (if you'll pardon the pun). 99% of the time, when asked, people are polite and say "I don't mind, whatever".
Edited by Holdfast - 8/25/11 at 12:09pm