markets and global communication

[Neal H. Walfield]

At Sat, 05 Nov 2005 12:49:46 -0500,
Jonathan S. Shapiro wrote:
>   4. Because market-based mechanisms rely on global communication, they
>      constitute a global communication channel.

Can you clarify this a bit more.  How do market-based mechanisms rely
on global communication?  My understanding of the power of markets is
that they are useful becuase they precisely don't require global
communication to find acceptable solutions.  Scott H. Clearwater
states in the introduction to "Market-Based Control: A Paradigm for
Distributed Resource Allocation:"

  A very abstract definition of a market is a system with locally
  interacting components that achieve some overall coherent global
  behavior.  The fascinating aspect of a market is that through the
  simple interactions of trading, i.e. buying and selling, among
  individual agents a desirable global effect can be achieved, such as
  stable prices or fair allocation or[sic] resources. . . . Their
  ability to facilitate resource allocation with very little
  information, i.e. price, makes them an attractive solution for many
  complex problems (v).

Thanks,
Neal