So reading TFA, it's simply ads for OneDrive/Office 365 (MS File Sync Products Only). Not general 3rd party ads like it makes it sounds. I still don't like the change but it's not nearly as bad as full blown ads.
Ad-like notifications for OneDrive do appear in File Explorer in the Anniversary Update, but people running the Creators Update are now seeing actual advertising.
This points out that there appears to be a transition from "Microsoft product ads" to "full blown ads". Quite worrying. I only use Windows in a VM, but still find it to be a very useful O/S for some things.
I know that one could make the argument that clicking the "chrome" button and seeing ads (ie. the internet) vs clicking the "files" button and seeing ads are not that different. But to me, they are worlds apart.
