Verizon is taking steps to conserve some of the rapidly depleting IPv4 global address space by implementing a technology called Carrier Grade Network Address Translation, aka Carrier Grade NAT, aka CGN. CGN essentially puts you and many of your fellow Verizon DSL customers behind a large router to use a private IP address in place of your (currently) public IP address. A private IP typically starts with 10.x.x.x, but could also be in the range of 192.168.x.x or 172.16-31.x.x. A public address is anything outside of that range (with a few exceptions you would never see for multicast, local loopback, APIPA, etc.).
Why does this matter to you? Have you ever had to open ports on your home router (Linksys, Netgear, D-Link, etc.) to allow you to host a game server in your home? Do you access an FTP server or maybe remote desktop into your home system while you're away? This move will interfere with those abilities by removing the ability for you to port forward. Fortunately, Verizon recognizes this limitation and offers you a method of opting out. Verizon also notes that this is only being implemented for their residential DSL customers. Business DSL and FiOS customers are not affected at this time.
If you are a current residential Verizon DSL customer I would advise opting out of CGN immediately to keep your frags flowing without interruption. For full details of this announcement and the opt-out link, head over to
Verizon's page about CGN.
Edit for clarity