There's many (perfectly legitimate) buyers out there for whom this would be a deal breaker. If you don't run the adverts through my server (i.e. including using

There's many (perfectly legitimate) buyers out there for whom this would be a deal breaker. If you don't run the adverts through my server (i.e. including using JS on my adserver) then you won't be serving my adverts. And in the world of media buying, that's not at all uncommon.