It's interesting how people refer to the blockchain as something indestructible, when it's just a database on several computers with known IP's. A physical attack against the owners and their property would work, especially when there are few witnesses like we have here.
Yes, everything on the blockchain is transparent, and the accounts downvoting content will sooner or later be identified (but not the individuals behind them or who paid for the attack). Now that you have a list of downvoters, what do you do?
If you downvote the downvoters, you achieve nothing, as reputation is meaningless - other people's posts are already collapsed and grayed out, and now so will be attackers'. What stops them to continue disrupting the network?
Ned and Dan will have to block their user accounts. Oh-oh... Steemit refuses access to the personal accounts of a hundred people, worth $100,000 each. What will happen next?
- Steemit is unusable, so new user registrations will diminish.
- Current users will have to regain their (useless) reputation, so their posts start showing up as non-flagged.
- New and current users will keep wondering if Dan and Ned won't cut access to their funds one day.
- News of Dan and Ned's single handed interference get out and the high price of Steem (which the evil Russian oligarchs raised by buying $10 million) starts to go down, as markets are extremely sensitive to conflict and speculation. After all, what could be worse for Steem than the realization that its own free network is not at all free, but under the ultimate control of two people, who can steal millions of users' money on a whim?