Traditional lines blur between banking and e-commerce

China is the scene of a growing rivalry.

In one corner is billionaire Jack Ma's Alibaba Group Holding Ltd, which holds the title as the country's biggest online retailer. And in the other are China's biggest banks.

This week, Alibaba launched MYbank, an online lender that will tap into Chinese savers' record $7.8 trillion of deposits and a banking revenue stream that is forecast to double by 2020.