I stopped CPU mining  operations due to the issues created by the mentioned users. CPU is completely impractical now. Realistically the devs need to either change the algo again to close off GPU operations, or make a GPU code openly available, though this option then opens up the opportunity for switching out operating code on Bitcoin miners potentially, thus meaning bitcoin farms could just re-purpose almost overnight and kill it in that way. At the moment though miners are losing interest because of the zero rate of accrual. If we have two miners dominating the whole thing for too long it could well kill Steem.