On my daily broadcast for KenRadio I fill in co-host Peter York who is a data networking expert explained that the issue with Comcast was their having a faulty DNS server. That likely led to this whole issue.
The problem wasn't AT&T's and this could have easily been Vonage or Packet 8 who got broad sided by the Associated Press. But the average user isn't Peter Yorke and would never have known. Nor would most technical support department staff know at a VoIP supplier.
Yorke, who plugged in the Sprint DNS settings to his router was working while everyone else was off line. That then begs the question if VoIP gateways need to be using the cable company's DNS or can actually use their own.