Interestingly, as far as I am aware none of the top 20 give any kickback to those that vote for them as a witness. So that's good news here! (Edit: I might be mistaken, jerrybanfield could be, but I don't have enough information on his actions to make a full conclusion.)

But if you go look at some other DPoS systems, you can see some degradation, with 'delegate pools', so we aren't immune to the possibility of it happening here.

To be honest as a new witness I didn't get in this for personal reward.

I'm glad you feel that way, and I feel the same way for sure -- and I believe that's how all block producers should be thinking. It should be primarily about the good behaviour of supporting the system. :)