As other have said: Don't do this. You'll invite even more negativity to your app and your company. Other users will be able to read through these negative comments and if you have plenty of happy customers, it won't affect your sales much.
As for the nasty e-mails: Ignore it.... If it is reaaallllyy nasty, getting threats and such, you may want to notify police. -- You received this message because you are subscribed to the Google Groups "Android Discuss" group. To view this discussion on the web visit https://groups.google.com/d/msg/android-discuss/-/j8_rOoLE-fIJ. To post to this group, send email to android-discuss@googlegroups.com. To unsubscribe from this group, send email to android-discuss+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/android-discuss?hl=en.