If Level3 (or Netflix) would read the Peering Playbook, they would see that they need to attract some upload traffic from Verizon to balance their flows, and get Verizon to upgrade the links (then, once the links are in place, they can drop the upload traffic). If I were Level3, I would find a backup service or image/video hosting site and convince them to let me advertise their IPs to Verizon/Comcast to balance the flows.
I looked for old level3 peering policies, and actually in 2004 they didn't mention balanced flows which was surprising, because most "Tier 1" networks have required balanced flows for peering for a long time.
If you don't like Level 3 paying Verizon/Comcast, consider the situation where Verizon has no backbone, and pays for 100% transit from a hypothetical Tier 1 provider. If Level3 doesn't have balanced flows (within usually a 2:1 or 3:1 ratio), most Tier 1's would depeer them as well (or refuse to upgrade circuits).