There is some confusion about what Comcast is doing when it sets up public
Wi-Fi using customers' in-home modems, vis-a-vis what Amazon's new data
"stealing" scheme is doing. There are big differences.
1) Comcast is setting up essentially a separate virtual LAN for the
public Wi-Fi that does not interact with your normal data flows.
2) Comcast is adjusting for that secondary usage so that it has no
impact on your usage costs or usable bandwidth.
Amazon is just taking your data without your affirmative permission, to
service their other customers.