I used to be an editor at Unisys and their style guide required all content to be tagged as per the following example:
Copyright © 1996-2008 Example Corporation. All rights reserved.
All those words were required. You could not drop any of them or use substitutes such as (c). I assume they paid copyright lawyers for that advice as I recall a lot of verbiage explaining why each word was necessary.
(I also had to make an entry in a company register every time such an assertion was made - it applied to software code as well as documents and website pages. I had to note the names of authors, programmers, including contractors.)
I don't think that other thread shows corporate usage correctly. The word "Copyright" always precedes the © symbol on the sites of major companies.
That doesn't mean that everyone in the company uses one style. :) e.g.
Copyright © 2008 Microsoft Corporation. Release: Thursday, February 7, 2008.
Copyright © 2006 by Microsoft Press Deutschland
Copyright 2008 Microsoft Corporation. All rights reserved.
© Copyright 2008 Microsoft Corporation. All rights reserved.
The Windows Server 2008 copyright statement [technet2.microsoft.com] is a treasure trove of variations, all on one page! Goes to show that publication these days is available to so many people in a large company that no editor could possibly get in the way and survive. :)