Update (12:55 pm ET): Akamai appears to have fixed the problem, and services including Steam are either back online or headed that way. Akamai said it will continue to monitor the situation to ensure that nothing falls out of place, but for now Steam appears to be fully back to normal.
We have implemented a fix for this issue, and based on current observations, the service is resuming normal operations. We will continue to monitor to ensure that the impact has been fully mitigated.July 22...