It's a pretty unsettling concept. From what your site says you say that you have full control of the device's requests as long as they are plugged in and at 70%+ battery... and that just sits wrong.
What gives an app the right to monetize a user when they are not even remotely using said app? What about legal liability if the malicious requests are sent from the user's phone causing damage somewhere else? Sorry I just don't see how a developer can "Deserve" to effectively turn their audience into a highest-bidder botnet when the user may not have used the app for days, weeks or months.
Thanks for your comment, your notes are definitely contributed for the discussion and here are ours:
You can be sure we already had massive legal research prior to the SDK development.
Residential proxy services are existing for years and you'll not find even one big corporate in the world not using such services.
You may try becoming a client, not only IP Ninja's but all of our competitors, it is not easy at all - we verify each of the companies that reach us out to buy our services so you can be calm as regarding to potential damage coming from your user devices.
What gives us the right? only the end-users, they get a very clear and transparent consent dialog, linked to a 3-lines EULA, they understand exactly what we ask them for and those who accept it (around 75%) understand that by accepting they contribute to the free apps development industry.
It is more common than you think... we can say that all providers in our industry are connected to more than half a billion devices around the world (mobile and PC).
In a perfect world, you wouldn't need to monetize your apps at all, everybody would be willing to pay for each app downloaded, but the world is not yet perfect, unfortunately.
It's ok to disagree, we're not forcing anyone to participate, maybe serving an endless amount of ads within the app is better, and maybe not - it is completely individual... Eventually, it's the developer decision on how to monetize his apps and the end user's decision if supporting the developer by joining the VPN network or not, it's a free world after all.