Yup, some countries have only these 3 payment methods. This should appear in countries where iTunes only sells applicaitons. From http://support.apple.com/kb/HT2001:
Shopping the App Store requires an iTunes Store account. When you create an iTunes Store account, you must provide a payment method for your purchase. The available payment methods vary by country, but typically you can use credit cards, gift cards, store credit, or PayPal.
In countries where the iTunes Store only sells applications, the accepted payment methods are Visa, MasterCard, and American Express. Other payment types such as gift cards, store credit, monthly allowances, and PayPal are not accepted. Depending on your App Store country, prices are listed in either US Dollars or Euros.
The thing is, for example here in Czech Republic, full iTunes content is available for me to buy, BUT I can still only link with Visa, MasterCard or American Express (what? in EU??). I think this should be reviewed for some countries.