AT&T is now handling SlingPlayer, Just like VoIP

AT&T apparently is handling the Sling Media application the same way it is dealing with VoIP: users can access either sort of application using a Wi-Fi connection, but not the 3G network.
The rule appears to apply to all AT&T smart phones, not just the Apple iPhone. Sling's "SlingPlayer" for the iPhone is available now, allowing users to stream their live television signals from their own Sling boxes at home to their mobiles, so long as their mobiles are in a Wi-Fi zone.
AT&T says the measures are intended to preserve quality of experience for all users, and there is truth to that claim, though the explanation is not likely to be accepted in some quarters.
Mobile networks are capacity constrained in ways that wired networks are not, for reasons ranging from simple available bandwidth to additional limitations added by the radio network and signaling overhead