but is it sustainable?
Billion dollar question right there ;)
I've tried to think of attack vectors, but aside from hacks (which I also doubt due to blockchain), I can't identify weaknesses or what could facilitate a massive drop in price. I think the price is seeking out equilibrium based on the rapidly increasing demand.
I think we've got a long way to climb yet
The key is new users, the attach rate of SP to new users, the ratio of SP:Steem extant, and the flows to and from the exchanges (b/c flows from exchange are likely Steem being powered up and taken off the market for awhile).
Is there a site that shows stats for powering up and down? Not individual users but all.
Good question. I've seen the number that 98% of all Steem is powered up. But the source of that, I'm not sure.
Don't underestimate the masses that will be buying soon when it starts hitting other exchanges!