The key here is governance.

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I think if you click into the linked post, you get the analogy regarding governments and governance. Web platforms have to concern themselves with governance of their users and the respective eco-system that their users operate on.

The point is less to be abstract or symbolic, and instead look at the concrete decisions they have to make. Corporations or general relationships do not have to consider these points to the same degree for survival.

In the past, governments would create policies, laws, and make decisions that would determine the well being of a citizen. Now, web platforms are more commonly making decisions of regulation, censorship, interoperability, which all fall in the realm of governments.

  "So as you watch the large web services evolve, think 
  about how they are balancing the relationship between 
  the state and the private sector? What does Facebook's 
  introduction of Facebook Credits say about its monetary 
  policy? What is Apples foreign policy? Do they act 
  unilaterally promoting their own proprietary standards 
  or do they act multilaterally embracing international 
  standards? What is Twitter's industrial policy? Do they 
  invest in state owned services or encourage decentralized 
  economic development? The choices these platforms make 
  reveal a lot about who they are, and ultimately how well 
  they serve the companies operating in their economies and 
  the citizens who live there."

Companies or corporations in general may have a degree of these problems, but not in a way that their survival depends on.