I see it as abuse on a few different levels @ecoworld does control all the accounts.
They are removing $100+ each week from the reward pool and only up-vote their own comments. Had they purchased the steem instead of it being delegated I would see this as a lesser problem. I'm personally still on the fence about up-voting your own comments in general.
Some of these accounts are newly created. There are users in the #help channel of steemit.chat just waiting to get an account to start posting and being a part of the community.
This could indeed turn into an issue of spam were more users have the means to signup such a large amount of accounts through the website and receive delegated STEEM.
And I have to wonder how they did it. I just checked 50 of those upvotes and they are on accounts created in the last two weeks! Several more that I checked were created since the middle of June.
It's a big issue. In the next HF I believe this will be addressed and the way accounts are created will be changed; however for the accounts that exist today I'm not sure if there's anything that could be done to stop that besides having a whale bot that can blacklist such accounts and auto flag their spammy posts until they eventually give up on doing that.