> It's really trivial stuff to do basic analytics on where your customers are coming from when they arrive at a website and it's not hard to see which ones are arriving because they clicked on ads and which of those translate into purchases.

No it is not.

If a customer came from brand bidding, you do not know if he would not have come to your website even without the campaign.

How do you calculate where a customer originated from, if he visited the site multiple times, sometimes through paid and sometimes through free channels?

You cannot blindly trust their claim that they are creating value - even advertisers from your own company are in on it.

I am speaking from my own experience working at analytics tools for a corporation, which has a monopoly. The product name is our brand. We are the only ones selling it. Every child knows it. Think public utility.

These people will still do brand bidding.