Google isn't becoming a carrier in the normal since, they are becoming a MNVO which means they are piggy backing on Sprint and TMobile. So this is nothing really to become excited about. For those that don't know what MNVO is, Mobile Network Virtual Operator.
Erm...
mvno - The
network is virtual, not the
operator: mobile virtual network operator. Big difference. They don't just sign people up and take a cut while Sprint or T-Mo does all the lifting.
^ What difference does it make exactly?
They don't have to build out infrastructure so much and can hit the ground running with a huge footprint really fast.
They are still gatekeepers and conduits not only for your data, but voice as well. All your traffic is going through their servers.
So the difference is speed and ease of implementation on Google's end. Their top to bottom control of traffic is no different.