Sport leagues, as businesses, are hard to quantize when comparing them to more traditional corporations.
A company that makes a physical product has complete control over its manufacturing and distribution. They can also set their prices according to the market's demand. Likewise, service industries maintain complete control over the services they provide.
Creative entities like music and movies have it a little tough because, while they control the creation of their product, they often have trouble maintaining control over distribution, but at least they have copyright laws to back them up.
an organization like the NFL, however, is in a whole other world. Their product is an image (both live action and visual representations such as merchandise). How do they control that?
With merchandise, its not to hard - their logos are trademarked and they license the use. In the past, they've also been able to control the live action by selling tickets to the game and licensing the broadcasts. But their product is more then just the 3-hour game. The live action, interviews and practices, happen every day of the year. Don't they also have the right to protect this "material" from free distribution? I say yes.
of course, on the other hand... the NFL enjoys free promotion and marketing through the media. News programs have segments dedicated to their product. When was the last time you heard on your local newscast, "and coming up next: news, traffic, weather and the Microsoft report" ? never.
So while I agree with my above statement about the NFL having the right to restrict their own products - i also think this 45 second rule is a shot in the foot. really dumb.