Microsoft Raises Roaming App Limit For Windows and Windows 8.1
Starting on October 9, Windows Store apps can be installed on up to 81 devices associated with a single Microsoft account. This will apply to all apps in the Store, for both Windows 8 and Windows 8.1. Microsoft is providing a set of APIs to build a service-side verification to set a limit in the event that devs won't be keen on the numerical change, but developers that decide to have the app enforce a constraint around the number of devices "must disclose that constraint to Windows Store customers and set expectations appropriately."
So, it's good news -- but why settle on 81? Quite the odd number.