All of the above. It could be a person from anywhere without a distinctly regional accent. The news person is the common example. It's what Veronica Corningston

All of the above. It could be a person from anywhere without a distinctly regional accent. The news person is the common example. It's what Veronica Corningstone refers to in Anchorman when she says, "But while they're laughing and grab-assing, I'm chasing down leads and practicing my non-regional diction." People that think they have this accent or that someone else has this accent will often refer to it as "no accent". It's not an ethnocentric viewpoint. Now, I definitely think the average person is not aware of how distinctive their accent really is and mistakenly think they have a non-regional one. But I do think it exists. Just to give an example off the top of my head: take Conan O'Brien. He's from Boston, went to college in Boston but does he have a Boston accent? Maybe you could pick it out of his voice, but the average person probably wouldn't and he certainly doesn't have a strong one.