> In this case, the unwritten expectation was that they weren't going to meter you and you didn't have to worry about overage charges, but that the 1Gbps should be thought of more as a burst rate than a 24/7 sustained rate.

Actually the written expectation was "unlimited" - without limitation. These so called "unwritten limitations" exist solely in your head, and are not suitable for companies to assume users inherently know.