If I thought the whiskers served much of purpose I wouldn't trim them - can't say I think those links put forward a very convincing case though.
For cats maybe but not dogs.
Has anyone ever seen a dog not carry on putting it's head into a tight space because their whiskers touch the sides ? I haven't - they tend to just keep on pushing and pushing.
Only one of my dogs has ever got their head stuck anywhere - Misty when her ball rolled through some narrow railings. She had really long whiskers back then - if she got any messages from them she paid absolutely no attention. If anything brushes past our hair we react - doesn't stop us getting haircuts - dogs react too if you touch their hair endings - doesn't stop us chopping off their topknots.
I don't think it plays any significant part in sense or scenting either - their noses, jowlels and wafting ears are what they rely on. Lack of whiskers has never stopped my 3 sniffing out fox poo, KFC bones and piles of vomit from a mile off.
Dogs whiskers - as much use as a one legged man at an ar*e kicking contest.