Like coderdude said above[1], whenever you see "All Rights Reserved"[2] you're seeing it in action.
1. http://news.ycombinator.com/item?id=3541501 2. http://en.wikipedia.org/wiki/All_rights_reserved
© 2012 Microsoft
Copyright © 2012 Yahoo! Inc.
© 2012 Twitter
"and the year of first publication"
About the presence of rogue engineers playing with copyright notices at will in big companies, some yahoo properties go through the hassle of manually updating the copyright notice every year under the explicit request from the legal department.
As many others have pointed out the whole thing is just a signalling mechanism, and not a strict requirement -- "(c) 2012" says, "Don't steal this stuff, it's copyrighted, and we have actively maintained this page through 2012 so we aren't a company from the stone age."