At Authenticated Digital, we built technology which analyzed each Javascript ad tag, and logged each partner that contributed to the ad being delivered from the advertiser to the publisher.
For example, a simple transaction could be:
Advertiser -> DSP -> SSP -> Publisher
If there was a middleman who was arbitraging ad spend (buying from one platform and selling on another), the transaction could look like this:
Advertiser -> DSP -> Ad Network -> SSP -> Publisher
The worst offender?
Advertiser -> DSP -> Ad Network 1 -> Ad Network 2 -> … -> Ad Network 1278 -> Publisher
Yes – the ad actually was bought and resold OVER 1200 times before being delivered to the page!