IANAL but for web pages, especialy dynamic ones, "the year of first publication" seems to be a flawed concept. You could as well say the page is first published everyday.
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.
Not unless it's the same content. Arguably if some of the content is old (old blog posts, tweets, etc.) then you should use a range of years.
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."
And when the legal department noticed the error they didn't want to go through all the hoops to get it fixed, as legally it has no meaning. Also, as we see many people seem to think that you need to update the year, so they might have done it on purpose even.
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.