The year is supposed to be the first year the work was created. You can do 2008-2012 if you want though (and let the end year automatically update). But since that's the assumption if you don't include the end year, there isn't any reason to do it.
The content of Facebook wasn't first created in 2012, so I'm not sure if you're correct. In fact, I've noticed that the majority of sites don't include a date-range. Regardless, thanks for the info.
Things aren't as cut and dry with legal traditions. I'm sure there are tons of scraps of legal language that remain in use only because it's traditional and few people know any better. Like some kind of legal shibboleth.
Like coderdude said above[1], whenever you see "All Rights Reserved"[2] you're seeing it in action.
It appears that you're correct, but I'm still having a hard time believing that the legal departments of almost every major company make the same mistake. That makes me think that there is something we're missing.
Copyright is automatic where it is automatic. In the United States you don't need a copyright statement. Also, no matter where you're from, "all rights reserved" is meaningless (post-Berne Convention).
It's (as I understand it) legally meaningless, but it's not "meaningless": it's a socially acceptable way to express the sentiment of "this is not open source or in any way something I am sharing with the public". Avoiding confusion is a good thing. It's like the opposite of a GPL COPYING file.