From what I can find:
"To buy files through the store,
a user must pay with an iTunes gift card or a credit card with a
billing address in Australia, Austria, Belgium, Canada, Denmark,
Finland, France, Germany, Greece, Republic of Ireland, Italy,
Japan, Luxembourg, Netherlands, New Zealand, Norway, Portugal,
Spain, Sweden, Switzerland, United Kingdom or the United States.
Other people can only download free podcasts and
previews."
