How do I know who has downloaded my application from market?

I want to upload an app in android market. I need to know the legal installations on devi开发者_C百科ces. So is there any information available to developers to know who has downloaded their apps from market. Because, one thing i am sure is that a person can not download an application unless he is not signed in.

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you need to use licensing

http://developer.android.com/guide/publishing/licensing.html

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Not specifically a programming subject, but if your application is for sale you can log into the Android Market publishing site and then click on the link to your Google Checkout account: every individual who has paid for your application will have an order entry with full details about who they are in the Google Checkout orders page.