Thanks for sharing this @transisto, this is an issue that really needs to be dealt with. Closed voting rings are something that only became apparent to me, but now that I know about them, it is very easy to see who is involved in them. This is a shame, because these rewards could very well be shared out betweem a lot of users on Steemit.
I have no issues with people voting for people constantly, in fact I don't really have an issue with the voting rings either; my issue is with people who only vote within set circles. If there are 5 different people that you upvote every day for whatever reason, but you also upvote 5 other users per day, I don't see that as an issue - in fact I have people that I vote for on every post because I think that their content is excellent and they deserve my full support, but I also upvote random good content.
I am not full sure of how to combat this, but I am currently playing out an idea with a few developer friends for a platform somewhat similar to Steemit, and have been addressing all of these issues with them, especially the fact of trying to regulate something like voting on a platform that is not regulated - we are looking at predefined protocols, but the issue with them is they can always be gamed, eventually.
Thanks again for sharing this.