if you use to many gatways it will be usability issue. If we talk about technical issues for users check this:
URL google: [checkout.google.com
The types of cards accepted through Google Checkout are based on the seller's location. Other types of payments, such as checks, money orders, and direct bank account debit, aren't currently accepted.
* Accepted only in the United States
** Accepted outside of the United States
Note: Google Checkout does not accept wire transfers/bank transfers or payments via Western Union/Money Gram, nor does it use any escrow type of payment.
URL Paypal: [cms.paypal.com
If there's a problem with your order, you're protected when you pay with PayPal.
We offer our buyers:
$0 Liability for Eligible Unauthorized Purchases when you meet our requirements
Refunds for incorrect orders or items that never arrive
A convenient process for resolving problems
URL Amazon: [payments.amazon.com
Send money to your friends and family using the payment information in your Amazon.com account.
You can send money to their e-mail address or U.S.
So, what you like needs some additional information:
4. eCommerce issue such as post-sales solving methods (return of money, frauds...)