One Person with a bot-net or datacenter is trying to dominate steem-mining. If you look at the witness-list you will see a long queue of miners who are waiting in line to mine steem, and as you can see on the next picture, one person is pretty much dominating that queue.
If this was Bitcoin, a guy like this, would be a danger to the blockchain!
But this is steemit - these 19 #witnesses make sure everything is legit!
I personally think it is incredible that one person dominates the entire mining queue, but - he is not making any threat to the steem-chain - this blockchain is really designed by geniuses. On the Bitcoin Blockchain it is all about everybody getting blocks at the same time - like a flock of elephants crossing a narrow door at the same time.
I could go on and on and on about how much electricity that is wasted on miners mining bitcoins and not finding a block, or how bitcoin-miners are paying the power-bill to the powers that are - the power-plant-owners, but I will not bother.
All system works the way they are designed :)