Sports, Twitter, and the 1st Amendment

I feel across a cool article on Richard Symmes entertainment blog about the friction between private sports organizations (cough - NBA - cough) and the rights of their players. The NCAA does regulate what its players can do, even in their private lives (to an extend)... is this simply the internet equivalent of this? Or is the NCAA overstepping their boundaries by becoming entangled in social media? (The peanut is neither a pea nor a nut. Discuss).