Monkeys aren't people, and the exchanges in the monkey "economy" are at   
best at analogy for a human economy.  As with all analogies, there are   
positive parallels as well as disanalogies.  The issue originally raised   
was whether the monkeys engaged in barter or monetary exchange.  That, of   
course, depends on what the essential characteristics of barter or monetary   
exchange are taken to be.  It won't do, however, to define the terms in   
such a way that historical periods in which exchange was largely conducted   
in gold and silver coin or fully backed paper are categorized as   
barter.  For that purpose, it is the lack of exchangeability by right   
(ultimately through some shorter or longer chain) into something with   
intrinsic value that is the most salient feature of money.  I take the   
monkey's tokens to fit that characteristic.  
  
I agree with Matt Forstater that human monetary systems typically involve   
infinite regress valuation.  This may be a disanalogy with the monkey   
economy, but it does not seem to me to address the salient feature in his   
original argument.  Also, the fact that I value money because I believe   
that you value money, does not imply that the money that I hold is your   
liability.  Chains of valuation of financial assets must be anchored in   
real goods -- sometimes they end in pork bellies; sometimes they end in   
dollars.  In our society, dollars are real goods -- despite the fiction   
that they are liabilities of the Federal Reserve -- because they ultimately   
supply a real service:  as Matt notes, they get the IRS off your back.  But   
notice that this is not because they are a liability that must be accepted   
by the issuer -- the IRS is not the issuer.  Anchoring the value of dollars   
in the payment of taxes is a sufficient but not necessary condition of its   
value.  
  
For example, when the Australians wanted to monetize exchange among   
tribesmen in New Guinea, they proceeded in two steps.  First, they   
conditioned the tribesmen to valuing externally produced goods, such as   
metal pots and knives, by giving them away.  Then they offered those same   
goods only in exchange for paper currency.  The natives had to obtain the   
paper currency by working in order to purchase the goods.  No taxes are   
involved.  Nor do the exchanges at Australian stores involve a right   
implied by the "liability" nature of the currency:  after all, the prices   
of the goods could change; certain goods may or may not be offered.  All   
that is needed is that the natives have a  belief that the currency would   
frequently enough serve as a means to obtaining the goods.  As I have   
described it, the situation in New Guinea is rather closely analogous to   
that of the monkeys.  Yet, it may seem to fall short of a full bodied   
monetary economy if the exchanges were always short circuits from   
Australian employers to native workers and back to Australian shops.  But   
if the natives begin to use the currency in longer circuits amongst   
themselves, then a full bodied monetary economy would be in place.  The   
monkeys apparently were not given the opportunity to develop such exchanges   
amongst themselves.  But like all laboratory experiments, the point was to   
examine some feature of reality by isolating it from others.  So, while   
there are positive analogies, there are also intentional disanalogies.  
  
Kevin Hoover