Open vs. Closed: What Does Open Really Mean?

The Open vs. Closed debate continues to bubble and boil around Facebook and the social networking site's attempts to extend its "social graph" out into the broader web. Is this move by the company truly open, or is it a cynical attempt to co-opt the rest of the web and aggregate value for Facebook — or could it be both? That all depends on what the term "open" really means. Can a company or a service be partly open, or is it a binary thing? Can a service start out as mostly closed and then become open? And is it OK for a company to be open with some things and closed with others?