BUT you have to consider, that even 0,2 SBD for people in developing countries is much money. So they will find it still worthy to open even more accounts to spread useless content to gain even a few cents.

This, right here, is remarkably important. I watched another content-for-pay site get taken down because of this very issue... three specific locations where making $100 a month would be "a really BIG deal" in your life. The warnings were ignored because the company was based in the US and the prevalent attitude was that "it was just small amounts," but it's remarkable how quickly a rewards pool can be drained when you have thousands out there "mining for fractional cents" 24/7...