Disable telemetry while you're at it: "Firefox Data Collection and Use" in settings. It seems to have re-enabled itself on some silent update. Sneaky bastards.
I would like to see any source that may exist on it having been silently re-enabled. I know telemetry is anonymized and totally harmless or whatever, but re-enabling it behind my back would feel like such a breach of trust.
Go interview people Mozilla. Less analytical data but you'll end up knowing your users.