Powering down doesn't necessarily mean they're going to sell the STEEM. Of course, any large holder will know that to realist the most from their investments will require taking a long term approach, and that includes gradually selling some of the stake.
In the long run, it is also beneficial to the platfrom to have a distribution more akin to the 'normal' distribution in terms of wealth. This will give us less volatility on things like price, and even the curated content.
One down fall is that the dollar value of posts will probably have to go. I can't see it maintaining this level of distribution and retaining that price mechanic . This is even when the author rewards are paying out only around a 3rd of the actual quoted dollar amounts in liquid sellable steem dollars.
" some of the stake."
Except they are not selling some, but all. That's what worries me. Wouldn't it make more sense, if they sold some, while kept some of their SP?
I wouldn't be worried if one was powering down %10, another %20, another %50 of their steempower they hold.
I wish some of those whales saw this and cared to comment what their motivations and plans are.
They have the option to power back up if they wish.
Essentially they must believe that growth of the site will endure the gradual selling of their stake. Remember, they can power down their whole SP but it is a controlled process. They won't be able to sell all their stake in one go. As long as they bring value to the site in proportion to the pace at which they liquidate their stake, then the price won't hurt too much. On the other hand, i'm not all against the price going lower as long as the fundamentals (ie the site, the development , the growth etc.) continues an uptrend. You just have to stick it out for a couple years.
Most people who start their journey on the internet and become 'successful' have had to spend considerable time growing along with the platform. But if the platform is really worth anything, then what's to worry?