Who cares? It's no different to accepting Euros but getting dollars in your bank account. The point is that they allow users to spend bitcoins (or Euros).
Widespread use of the Argentine peso isn't critical for its success (a strong economy and good monetary policy is). Widespread use is, however, critical for Bitcoin's success, since it relies on a network effect of merchants and consumers.
It certainly isn't bad news.. not to say ARS isn't likely doomed; but there are currencies not on that admittedly-long list of amazon accepted currencies.
