Yes, because the examples you give already have a solid reputation.
You can get away with it when you are "the government .gov", but if you are "small start-up.com" and I want to invest in your risky stocks and all I get is an "Oops page" when I want to know a little more about your dividend policy, I'm gone.
For me it depends on where the link originated. If it's a 404 within your own site, that shows sloppiness that will make me question your ability to run a business. However, if I get a 404 on a link from an external site, I'll assume things have been reorganized and try to find the new location myself (while wondering why it was moved). Changing URIs without setting up forwarding is so common I wouldn't give it much thought.
You can get away with it when you are "the government .gov", but if you are "small start-up.com" and I want to invest in your risky stocks and all I get is an "Oops page" when I want to know a little more about your dividend policy, I'm gone.