Probably the best way to remove this is by improving the ranking algorithm. For once, I think Google did it in a better way than Apple. On android, a bot system wouldn't work as efficiently. The first thing google did well is you can't easily download an app with your computer, you have to download it from your phone. The second think is Google's algorithm. I think Google nailed their algorithm, as opposed to Apple's. It takes several days for an app to climb, even a week on android whereas with apple's algorithm, an app could be skyrocketed to #1 in a day or two. The third thing Google did well is that their algorithm takes into account the usage. So if you download an app and delete, it will not be counted in the downloads. I think they also weigh their algorithm with more factors such as how long does the app stays on a phone, etc... I think Apple should definitely revise their algorithm, even if they had to instrument more the usage of every app.