Down-votes: Steemit's Achilles' Heel?

Introduction

I see that our favorite flagging account has been sold and is back in business. It's currently not a big deal, but just an annoyance. There's already at least one other bot following it around and counter-voting to balance the scales. But, it occurs to me that this reveals a potentially serious competitive attack vector against the platform and its users. Sorry if this is rehashing old ground, but if this aspect of down-voting has been discussed here before, I missed the discussion.

[Image Source: Pixabay.com, License: CC0 Public Domain]

Attack Scenario 1
Imagine a year or two from now, steemit (or one of the other gateways to the steem blockchain) has made serious headway into the social media market, and one or more of the big competitors starts feeling threatened. What could be easier for them than to power up a couple anonymous accounts with a large war-chest and launch a strategic down-vote campaign in order to drive away users, and reduce/eliminate their competitive threat?

Attack Scenario 2
Imagine a time in the future when dissidents from a country with an oppressive regime begin using steem's censorship resistance to publish the details of the oppression on the Internet. How hard would it be for their oppressor to fund a sock-puppet account and use down-votes to mute the criticism? (Remember NedaNet?)

Attack Scenario 3
Imagine that artists and musicians posting on steemit start getting traction and taking away customers from the major media. How hard would it be for industry groups to power-up and anonymously use down-votes to shut down their competitors' funding streams, and drive those users away from the platform?

Possible outcomes:
(i) The down-vote campaign fails and the attacker's investment holds or gains value, in which case they can just continue the campaign indefinitely, and even expand it until it succeeds.
(ii) The down-vote campaign succeeds, and their investment loses its value, but they are rewarded by achieving the desired reduction in competition.

Conclusion
If we use our imaginations, I'm sure we could come up with numerous other scenarios where a well-funded adversary could use the downvote to harm or destroy the platform. Are any of the current steem whales prepared to launch a counter-voting bot against a multi-billion dollar corporation or a state actor? Will they be ready to do it when the time is at hand? Or maybe we can just count on the financial Goliaths around the world to play nice when faced with a new competitive threat?

One mitigating factor is that a well-funded actor would drive up by the price of steem by purchasing their war chest, which would also strengthen the existing whales. I have doubts about whether that's enough of an immune system, though.

I have been persuaded by discussions here that there are theoretical and rarely encountered situations where down-votes truly are helpful, such as the crab bucket scenario in the whitepaper, but does the up side of down-voting really outweigh the down side or does the down-vote give a well-funded adversary a convenient lever to implement a denial of service attack? I'm not so sure.