I don't care much about e-sports, but I find the current controversy over streaming restrictions on professional-level League of Legends players fascinating. As officially confirmed by Riot, pro players are required to agree never to livestream themselves playing any "competing product" for the duration of the upcoming professional season. The forbidden list includes every current Blizzard franchise, other current and upcoming MOBA's, the World of Tanks/Warplanes games from Wargaming.net, and the canceled-during-beta Warhammer Online MOBA Wrath of Heroes (good luck "live" streaming that one).
This type of restriction is almost certainly within Riot's rights, since no one is forcing anyone to play League in general or participate in its competitive play in particular. As the run-away leader in this particular sector, they can likely get away with the move, regardless of rational arguments that it's not a good idea or in their long-term interest. Nor is it entirely without precedent - Bioware's official fansite program for SWTOR restricts sites from promoting other products or using any advertising, in exchange for a link on their official listing and possibly other perks (e.g. in the past fansites got exclusive dev comments).
The thing that resonates with this policy is that it's not so different from the position that regular customers find ourselves in every day when service providers (including but not limited to MMO's) do things that we don't like. In some ways, the real victims here are NOT the professionals, who are being compensated for their commitment, but rather the viewers of streams that will be less interesting to watch due to the restrictions.
You always have a choice to walk away, and your choice is almost always going to hurt you - by depriving you of a service you thought was worth paying for - more than it hurts the company that made the decision you disliked because it was in their interest to do so. This particular case just had the misfortune of making it obvious how little power the customer actually has.