Amazon will soon be a trusted Root CA. To this end Mozilla Bug #1172401 was filed a while back to get into Mozilla's trust store.
Along with 4 of their own Root CAs they've included a fifth one (Starfield Services Root Certificate Authority - G2) to be trusted again.
Why would they include an already trusted and working Root CA in their application?
See comment #9 on that bug from Peter Bowen at Amazon:
It also includes one additional root CA already in the Mozilla program which we wish to have enabled for EV certificate issuance.
That suggests that the root was already included in NSS, but not enabled to issue EV certificates; this is a request to change that.
Quote from comment #21:
I am now opening the public discussion period for this request from Amazon to enable EV treatment for the currently-included “Starfield Services Root Certificate Authority - G2 certificate, and to include the following 4 new root certificates, turn on the Email and Websites trust bits for them, and enable EV treatment for all of them.
