> Why should any corporation let you visit their premises without suitable assurances?
Correct me if I am wrong please, but it sounds like you are saying it's okay to trust corporations who are the subjects of media scrutiny to be the 'gatekeepers' of information, setting ground rules and defining what may or may not go into a news article. This is a horrifically bad idea if you care about journalistic integrity.
No harm in the corporation asking for that level of control, but I do not believe savvy journalists would accept. It is their (or their editor's) call to make, they must decide what the story is, and where the public interest lies.
Fair point about Nikon though, I think if you have a top-secret part of your factory that's just got to be permanently off-limits. Why risk it?