That's not as trivial as you may think. When a company needs a lot of sales on the Google market to pay its employees and continue to exist, piracy may quickly become the problem number one.
I know its not an ideal situation, but even if companies like Microsoft, Adobe etc have been unable to prevent this, how would indie devs like us combat it without Googles support.
On security forums, it is said many times that Android offers currently no real protection against piracy, contrary to iOS, and the level of code protection or data protection is far below what we can find on Windows games for example.
This is true. Google were going to introduce device-based encryption of apps but they turned it off due to problems. That was one step in the right direction, and two steps back.
That means the companies must use or invent new ways of earning money on this platform. One of the way I'm going to use personnally is to provide a plug-in to unlock the free version (as Winamp does), so the code of the full version is not in the public free version. Only registered users will be able to distribute a full cracked version. I can do the same thing with data. Only registered users are entitled to download data from a specific area on my server. Others can't download anything.
This is not as easy as it sounds. Anyone can download your registered plug-in and copy the apk and refund it. So now they have the full version, unlinked to the market. How hard was that? Short of having a webserver, a login mechanism, and internet connectivity in your app there is very less you can do. And even this may not be a foolproof solution, since I dont know if there is a way to link a buyers purchase to an ID on your webserver?
Eitherway it is a question of how much time, effort and money are you willing to invest in anti-piracy measures and whether it is worth making another app in that time that covers up your losses.