The Microsoft support site says you might get an error message when you try to validate Office by using Office Genuine Advantage: “Why didn’t my computer complete validation” or “Error code: 0x8018111”. They give the following explanation:

The Office Genuine Advantage (“OGA”) program has been retired

This is awesome news for anyone who has been trying to run Office on dynamic hosts in virtual environments. Every time I started Office (basically every time I started a virtual machine) it would throw up a message with something like “Hardware change detected; you need to validate your copy of office using genuine advantage”.

It was particularly annoying at conferences where I could start my presentation only after I clicked “Ignore” on the license prompt.

I complained many times directly to Microsoft so perhaps it is this kind of issue that killed OGA.