if you powerdown you don't receive "interest"
This is the most important point i wrote about it few days ago.
https://steemit.com/steem/@snowflake/there-is-a-big-flaw-in-steemit
Obviously the whales are not gonna like it but it is necessary to prevent the value going to nothing. As a whale said above they have no incentive to not power down, so Ned give it to them!