Quoted from the Kong help page…
What are MochiAds, and why are they turned off on Kongregate?
MochiAds is an in-game ad network that allows Flash developers to generate revenue every time their games are played on any site. Kongregate has a partnership with Mochi Media to disable MochiAds for games hosted on kongregate.com. This in turn prevents multiple ads from appearing and allows us to negotiate better rates from advertisers that we pass on to our developers.
Although MochiAds are not displayed on kongregate.com, we highly recommend their services for all Flash game developers. MochiAds is simple to set up and generates revenue every time a game is played no matter which site it’s played on… even if it gets copied to thousands of different sites all over the Internet.