Appears #T-Mobile / #Sprint ( and #US_Cellular, a smaller carrier which partly rides on Sprint's network ) are having problems with both voice and data connections.
It was earlier thought that #ATT and #VZW were also affected, but the article says that is not the case.
Rumored to be a DDOS against #ATT, #Verizon, #T-Mobile / #Sprint ... if so, the others seem to be weathering it well. T-Mo/Sprint seems to be having some problems.