Interesting that this came up on a Tuesday, because it was discussed at length many moons ago by a lot of us before the forums existed. I just scrolled through: Uncle Joe, Jeff, Alex, Lightnup, Paul Rushing, Dennis Galbraith... some guy that went by JL that couldn't disclose his real name because he wasn't sure if his employer would still employ him... ah, the good old days 
The interaction on this old blog post from 2008 birthed the forums in my opinion, and as much as has changed, here we are discussing monetization of user-generated content (dealer inventory) and the appropriateness of "leaks" that may distract the user (ad placements) almost exactly 10 years later!
If you are up for a trip down memory lane, this is a good one: https://www.dealerrefresh.com/blueprint-series-third-party-lead-providers/
I agree with you [USER=4695]@reverson[/USER], the portals will respond to the requests of the dealers, they ultimately have to. Without dealer inventory, they don't have content. Without content, they don't have eyeballs. Without eyeballs, they aren't monetizing that ad real estate anyway.
That is eventually what happened in 2008 when dealers were concerned about links to affiliate industries on the VDP. I'd guess the equation resolves in the same way in 2018.
