iClarified reports that Apple has warned iOS app developers that any attempt to manipulate App Store rankings or reviews employing third-party services could result in loss of their Apple Developer Program membership.
Adhering to Guidelines on Third-Party Marketing Services Feb 6, 2012
Once you build a great app, you want everyone to know about it. However, when you promote your app, you should avoid using services that advertise or guarantee top placement in App Store charts. Even if you are not personally engaged in manipulating App Store chart rankings or user reviews, employing services that do so on your behalf may result in the loss of your Apple Developer Program membership. Get helpful tips and resources on marketing your apps the right way from the App Store Resource Center.Apple's warning comes hot on the heels of reports that developers were buying their way to get their apps featured in Apple's top 25 list.
For $5,000, said company will allegedly utilise bots that will download a developer's app over and over again until it has broken into the top 25 charts. At this point, the developer's app will have received sufficient customer exposure to attract downloads from real people.
According to a Touch Arcade forum member, some of the top developers were already using this service.
Apple recently also started kicking out copycat apps from the App Store.
[via iClarified]

real developers already tried this that means angry birds was the same then they cheated to be the best then
So if I have competition all I have to do is manipulate their app rankings and get them removed… sweet!
Thanks for the warning, said the developers ;p