I see this type of thing not as decentralization backfiring, but rather as a failure or rather a shortfall in achieving it.
The point of decentralization is that power not be concentrated to individual entities or groups in the first place. That people with resources can arbitrarily purchase undue influence and power, and abuse it to suppress content is completely contrary to the level playing field that decentralization is intended to create.
I guess there are two levels to decentralization in Steemit, First the system level - where the architecture of the network and blockchain, and IPFS, and its implementation prevents hijacking and implements a consensus system to help ensure its evolution is to serve the goals of the platform at large. The second is the social level, where the participation, interaction mechanics and capabilities that the system provides its users cannot be "gamed" or manipulated to override or unduly influence natural consensus of the community at large.
So I think the scenario described here is exactly a failure to implement decentralization, not a consequence of decentralization itself.
As long as power and influence can simply be purchased rather than exclusively earned through community approval, or that influence of one user over others can create extremes in asymmetry to the extent that they enable abuse by individuals or small groups, this sort of thing is going to be a risk and a weakness.
Its very tricky to predict rules and economics that avoid being gamed in unfair or authoritarian ways. A million users is potentially a million minds fixated on goals that a few hundred developers don't intend.
disclaimer: I'm a steemit n00b still - my opinion is based on my general knowledge and I could be misunderstanding about Steemit specifically.
It looks to me so far like Steemit has done well for being this early in its evolution but still has to address these kinds of things and hopefully it will develop over time to do so.