Some of these domain parking services will automatically optimize your domains based on what people search for.
In some cases you can be paid when someone simply views your site (pay per impression), or when they click (pay per click). Other services pay if a person fills out a form or buys something (pay-per-action).
RPM (revenue per thousand impressions) is not the whole story. Some domain parking companies includes live newsfeeds to keep people coming back to your site. Some services makes it easy for you to use one-click landing pages, while others do not.
Active Audience and Gold Key, try to keep your domain listed in search engines. Results have been mixed. Many other services result in domains dropping from search engines.
Traffic from Asia does not monetize well on most of these sites. Sedo, Traffic Valet, and TrafficZ seem to do better than others with international traffic, especially European traffic and even some Asian Traffic.
Stats are updated in near real-time on some services, while others update once a day.
Sedo,and NameDrive and Fabulous offer additional services, not just domain parking income.
