I kinda talked about it here

https://steemit.com/steemvalue/@truthforce/open-letter-to-steem-stakeholders-what-adds-value-to-steem

Bidbots or SMTs can cause more centralization. At some point an un-optimal amount of centralization is reached and that is when there can be problems.

Of course that is only if the centralizing forces want to harm steemit,if they never do a 51% attack or take servers down or go after anyone then it isn't exactly causing an issue.

I am more worried about SMTs than anything else. For example, on Ethereum 80% of ICOs are scams and like 15% completely fail due to incompetence. We will see some huge scams happen when SMTs come out.

On Ethereum there are projects that make 100s of millions of USD pretty easily. Semi decent looking website, lots of shilling(they pay shills in tokens), "dev updates" frequently, etc. Then they turn out to be scams or just trying to make money. A few hundred million USD worth of SP is a lot.