Which mobile payment services are currently popular, and what makes them successful?

WeChat - hands-down one of the hottest mobile payment services. Its a wallet. 355 Million active users as of end March 2014. Its in China. They do more business that any of the other wallets in the West. Its 100% mobile. Its got tons of features. You can pay for pretty much everything with it. Its carrier and bank agnostic.

Some articles to read about it:

• WeChat is going to be huge for payments (unlike WhatsApp)
  
• WeChat Payment and Alipayment Wallet Strike
  
• WeChat brings new weapon to mobile pay war
  
• Enrich your wallet via WeChat in Spring Festival
  
• Do You Know About WeChat?
  
• Tencent: The Secretive, Chinese Tech Giant That Can Rival Facebook and Amazon