One might think that such a rapid increase in price is an indicator of a bubble formation and a soon bubble popping...
I think this is just a simple price discovery taking place. Ultra-low market-depth makes rapid price swings to the up- and downside easy. So it might tank 80% and then rise 400% again in short time.
But I think that the majority of people buying are in for the long term. So they buy the Steem and in order to escape inflation they switch them to Steem Power, without the possibility to flip them an hour later, even if the price doubles, they cannot do it.
I read in the White Paper that 98.5% were actually not available for selling when the white paper was written, I suppose since then this percentage has changed, but do not know where to look up which percentage currently is locked up. If this were the case right now it should be easy to reach new heights.
The concept to me looks brilliant, in every aspect.... only the reddit aspect justifies 4 billion... I think they will soon loose many communities to Steem... then we have this fabulous payment function which really opens up the sky in terms of valuation in conjunction with the possibility to earn interest. How much money might go in there if banks and negative interest rate policies cause havoc?? Banks raising commissions for basic stuff to absurd heights?
The Reddit user capture is the best... What if half of reddit users post on steem? 4.5 Million users, with their network effect for the payment side and mouth to mouth publicity? How many has Bitcoin acquired in the past 7 years? 1 Million? Steem can go viral and perhaps do this in 3 months...
Let us be honest... Bitcoin's model is shitty in user adoption and user motivation compared to Steem... here people can earn Steem, just by providing some value to the community, in the form of votes, comments or posts. They enter into the Steem World and can be a stakeholder without investing a penny in Steem or Mining equipment, nor technical knowledge.
Therefor, I might sound a bit optimistic, but I think ethereum is not the last coin to be overtaken... Bitcoin has its only advantage in the strong volume in USD and CNY all over the world. Steem has to allow for multimillion USD investments without much of a price move. With less than 5% outside in circulation, this might have to have a 10 billion marketcap to be able to do this function. But the price discovery might quickly go up to this level and then bounce up and down around 5-15 billion.
Many people will pay attention and study Steem at this point. And whoever studies it will get to the conclusion that 
This is only my opinion, please share your comments below and perhaps help me keep calm and cool down a bit.
I am so excited! :)