DirectAds is the LinkedIn® version of Google AdWords. The new service was launched in July 2008 by the company. They provide a simple interface and some degree of audience targeting. Jack Chou has written a good blog about this.
The idea behind RainKing is simple. RainKing employs dozens of human researchers to find managers, decision makers and executives in larger companies. This is kept in a database which clients can subscribe too. The added costs of manually vetting information (as opposed to using online spiders) is shared amongst Rainking subscribers through a subscription fee model.
