Stack Exchange made the brilliant move of having disparate communities with a defined (and passionate) audience for each. This makes selling targeted advertisin

Stack Exchange made the brilliant move of having disparate communities with a defined (and passionate) audience for each. This makes selling targeted advertising much easier. Ex. Stack Overflow is probably one of the best places to reach developers with job ads—hence they can charge a lot more for that than generic display ads. This is all pure speculation, but I wouldn't be surprised if Stack Exchange's RPU would be 10x Quora's.