the beauty is that everyone want to do re-attribution, so they can buy cheap and sell expensive. if I send a bid to google with a random browser id, it will as

the beauty is that everyone want to do re-attribution, so they can buy cheap and sell expensive. if I send a bid to google with a random browser id, it will assign a new user on the spot (we wont be lucky to match a valid user as in your example) and all goes on normally.