Apple has sent a stern warning to developers who try to inflate their App Store rankings.

“Once you build a great app, you want everyone to know about it,” the company announced to developers last night. “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.”

App Store rankings are based on a closely held algorithm Apple has developed. The algorithm is believed to include elements of an app’s download figures, news articles about a respective program, and whether it has been featured by Apple. User ratings also appear to be a key ingredient.

Getting into the Top 25 in Apple’s App Store is a near-obsession for developers. The apps that make it into that list generate far more revenue, and usually help companies expand their sometimes-small operations into real businesses. Angry Birds developer Rovio is a huge business today partly because of its ability to find its way to the Top 25.

Developers hoping to be the next Rovio have been hiring third-parties that focus solely on improving an application’s ranking in the App Store. Some of those services do so through legitimate means, by promoting applications and increasing awareness. However, as Apple points out, there are some services and developers attempting to game the system by adding fake user reviews that celebrate a title’s features.

Last year, Apple made waves by reportedly changing its ranking algorithm to give more weight to apps in certain categories. Social-networking applications benefited greatly from the modification.

Developers who didn’t benefit so greatly have relied upon the services of companies like Flurry or TapJoy to help boost their rankings. TapJoy’s advertising network for developers, for example, helps get apps in front of users. Last year, TapJoy said its program can push as many as 100,000 new downloads a day.

Apple did not immediately respond to CNET’s request for comment.