I did watch the show and learnt a lot. Someone mentioned on there that a whale could just come in and buy up all the liquid Steem and become a complete nightmare for the platform. Like you said, it hasn't happened because someone hasn't had the desire to do it.
There are many, many incognito rich people lurking in the Bitcoin world. One of them could smell the Steem blood and bite big time :)
I know of many on the fence about Steem.