Anonymous tracking is already part of the URL. The ?utm_source=unfck part of the URL helps Mozilla know how many people installed Firefox from that link.
You click the link. You get an ID assigned to you. You install the app. It calls back home with the ID and a list of specific apps on your Android.
This tracking is happens continuously. You have to go to the settings and toggle the data collection off.
In case it wasn't clear, I am not complaining. Analytics has its place, but the Unique ID's are a bit much, especially when they want to unfk the internet.