Unless I'm worried about search engines (e.g. public websites), I don't bother at all. A warning on the screen would be good manners, if you have the time to spare...

Most common users will not disable JS (at least not on purpose), and "super users" should know better. There are better ways to stay safe/anonymous on the internet.

This is only my personal opinion, of course. I'm not the type of person that likes to please everyone at the cost of my own "blood". Vast majority is fine by me :p

I plan my sites with all animations before building the actual thing. Then I make it work without JS (no animations, AJAX loading, etc.). In the end, I add all the JS which makes the page look good. Especially in the age of drive-by malware on websites and privacy-harming user tracking I know a lot of people who deactivate JS with browser plugins. If a site does not work without JS, they will not bother with it. I think, websites must work without JS, today and in the future as well.

Forget about SPA... how about using modern UI frameworks? Got Twitter Bootstrap? Using the menu? Have a dropdown in that menu? No JavaScript? BOOM!

On the plus side, cnn.com is wicked fast when JavaScript is disabled. LOL!

Very nicely asked. Apps written in Isomorphic style won't suffer this problem. If the views are both server side and client side this will work perfectly fine even when the user disables the JS.​