A viable world wide online payment method is mandatory for any internet user who wants to do business. Credit cards are the first option when you do online shopping or buy services, but they are not a solution for b2b or user to user transactions. Checks are history due to posting delays and Western Union is just too pricy. I will list below some of the most used online payment methods:
1) Paypal. Although it may not be the best, it is the most popular so I decided to start with it.
Advantages: The biggest advantage is the high number of users who use it, specially from US and Europe. Pay pal is quite easy to use for both user2user transfers and shopping carts or payment buttons. You also can easily create donation buttons.
Disadvantages: It is still not available in many countries or it is only available for sending. Paypal is target #1 for scammers and fraud. Some accounts get frozen for no reason and it takes ages until they get back to function or they eventually remain frozen. Some blame the high fees, but I think they are reasonable.
Advantages: Very low fees. The system is quite secure. They move fast with the bank transfer when you decide to withdraw. Although they do lock accounts, if you are a legit user they will listen to you and do some verification and eventually you will regain the access to the account.
Disadvantages: Moneybookers delays non-European customers. For new customers the verifying process can take some days. When you have problems it may take weeks until they solve out, but they usually solve out.
Advantages: It's backed up by gold, so it's like owning gold, therefore the balance in your account will always (almost) get higher without doing anything. It's very secure and they don't reverse transactions so once you get the money, it remain yours. It's worldwide available and you can create as many accounts as you like. Also it's completely anonymous.
Disadvantages: Sometimes hard to fund or hard to find trustable e-gold exchangers. The exchangers may have too high fees. The same when you have to withdraw.
Advantages: You get a nice plastic ATM card which you can use to get your money out of your account very quickly. You can also do wire transfers. World-wide available.
Disadvantages: They don't actually have shopping cart options or payment buttons, making epassporte unusable for online shops like sites. It seem to be very popular among affiliate marketing, used to pay subaffiliates.
Advantages: You get the ATM card the same as with epassporte. Available worldwide and you can use a variety of methods to fund your account: credit cards, paypal, wire.
Disadvantages: Can be used only for user to user or business to user payments. It's quite unpopular, few people know about or use payoneer.
Advantages: Strong security with many options of preventing fraud. No reverse transactions, reasonable fees.
Disadvantages: Good support only for russians. Hard to withdraw for non-russians.