I am curious is there any legal force in a statement like Copyright (c) MyDomain.com. In other words, the copyright holder is a domain name or the owner of the domain.
Copyright exists whether they make that statement or not. Giving such notice informs the public that the work is copyrighted, who owns it, and when it was published. If the work is infringed, the defendant will not be able to use an innocent infringement defense.
There's nothing special about using the domain name, as it's probably the name or DBA of the business that owns the domain.