Yes if you are Google and you keep track of all of these things you can quite accurately translate those metrics into potential sales.
Especially when you can build Plus Ones profiles for every phone every made then correlate that to actual sales figures. It's not 100% accurate but it's certainly accurate enough not to go out of stock in 1 hour.
Its Google entire business model last time I checked.
We don't know how many units were shipped. We don't know if Google is celebrating this or if they knew this would happen. It is possible that LG has supply chain issues and they can not crank out phones to meet demand.
You don't know that it was a stunt. It is possible they sold many phones. I really doubt that 8600 likes translates to sales numbers. There is no way of knowing if Google sold 500 or 2 million phones before it ran out of stock. It is also possible that LG does not have the production capacity meet demand. It would be a marketing stunt if Google is intentionally creating a supply shortage, but I doubt that is Google game. Then again, we won't know until Google releases a statement about how Nexus 4s have been sold.