Disaster 1: Undesirable ad placements
The most important feature of an ad network is the level of transparency that they practice. This is crucial to a successful campaign, as ads may appear on questionable sites or next to questionable content, hurting the credibility of the advertiser. When working with an ad network, there is often the inability to drill down on a site-specific level, and it is important to remember that long-tail inventory often includes blogs, sites with strong perspectives, user-generated content and social networking sites.
We have all been caught in a situation where our ad messages show up next to political comments, foul language or adult-oriented messages. You try to avoid this placement by excluding it in the insertion orders, but with user-generated content or interactive tools such as user comments, it is becoming more and more common.
How to avoid this
Placements such as these can be avoided if you establish a high level of transparency with the network upfront, making it clear which sites your ads will be placed on.