As a junior media negotiator, I tended to think of media buying as a zero-sum game; one side had to win and the other had to lose. As a more seasoned professional though, I have learned that the best deals in digital advertising are win-win scenarios. Both sides, both the seller and buyer, come out ahead.
However, there are some deals in advertising that are just terrible. Some are bad for one side, while other deals are actually bad for both sides. A terrible deal is more than just a high CPM. Rather, a bad deal in digital advertising is one where either side feels they did not get what they wanted and, quite possibly, paid a lot for that inconvenience.
The worst deals tend to be overly complex; one side does not really understand what they agreed to. While some complicated deals make for great ad campaigns, others just become hopelessly mired in confusion. The worst deals are confusing, costly, and complicated. Understanding what you bought, how to measure it, and what the data mean is the key to avoiding bad advertising deals.