Well, I have to say I'm a little more for the no refund policy after reading this.
They are safe. You can't hack them.
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Wow, I knew Android piracy was bad, but I didn't realise it was that bad. The worst part is that whatever DRM or whatever you add, they'll crack it in days Tools like apktool or apk-manager or whatever, while designed to create mods and themes etc. for apps, make it all to easy to reverse engineer apps. Sucks, but I guess that's "how it is"
EDIT: It's not hard to see why many devs turn to putting ads in their apps and releasing for free.
You probably implemented that LVL example given in the Dev Help. That one is pathetic and my blind grandma could hack it with both hands tied behind her back. In fact there are scripts/programs out there that do it for you automatically, so every schmuck script kiddy can do it.
If you want to use Google's LVL service customize the library as described here: http://android-developers.blogspot.de/2010/09/securing-android-lvl-applications.html
Crazy stuff..Update :
12 days in Google Play
Total users installs : ~100
Pirated version installs : 24000
Hey did I see a galaxy pocket in your sig?I read that 3 major Android piracy sites were shut down not long ago.
Sent from my jelly bean