What recourse do you have if Apple or Google bans your popular app?

I have a fairly popular app on iOS and launching the Android version soon. I read news to today about a developer whose really popular app was banned by Google just because they allowed their users to remove ads by paying with paypal:

https://plus.google.com/109338406398631174189/posts/NFZAm8MDpjz

This sort of thing really makes me think that I should have a contingency plan if something like this happens. What would you suggest are some ways to salvage an app if something like this happens, or is the business completely over with once something like happens?

If you're not even on the market yet, this isn't worth worrying about. You're better off spending your time on making sure that it won't happen -- reviewing policies, re-evaluating any non-standard practices of your app, making sure you're building on a platform that's worth it (sustainable or not), etc.

Fast forward a few years and if you've had enough success that it makes sense to think about contingencies, some things you should do are:

• Build relationships with Google Play folks. Attend Android conferences, follow and interact with them on twitter / G+, etc. If something goes wrong with Google, personal connections are often the only way to get anything resolved.

• Prepare your appeal thoroughly. You have one shot at getting the issue reviewed, so make it count. Particularly put effort into updates you're making / will have ready to go to make your app policy-compliant if given the chance.

• Diversify ahead of time, leveraging your success on each platform to help with the next. Android users have iPhone-using friends (or iPads themselves), and vice-versa. Amazon's App Store does provide some additional market opportunity for Android Apps.

• Own access to your users. Being removed from an app store shouldn't cut you off from your existing userbase. Have emails, ability to push notify, etc. Transitioning users (e.g. to a new, policy-compliant app, or to a Amazon or a web version) can suck, and you will no doubt lose many, but that's better than losing all or not being able to at least inform them about what's happened.