Originally Posted by Wizzo

The reason most big tubes and many other publishers and advertisers use a broker, and usually it's one like Exoclick which uses a ad server, that can geo-target the ad spots to best monetize them.

For example, you probably are only interested in English speaking premium countries, so you can buy that traffic, then someone interested in South American can buy that, someone looking for German can buy it, someone wanting India buys it, etc... So the overall value of the ad spot will be higher because all segments of the traffic are being monetized rather then selling to one person who is limited to what percentage of the traffic is valuable to them.