Move over PayPal: There’s a new e-commerce middleman coming to town. In October, Amazon unveiled “Login and Pay With Amazon,” which allows shoppers to use their Amazon account to facilitate a payment to an online retailer … even for transactions not being made at Amazon.com. Like PayPal, the vendor must also have an established “Login and Pay” payment-receipt account in order to receive that payment. With an established name like Amazon, however, it’s not like those e-tailers are going balk at the new payment venue. But what about PayPal’s dominance in this space? The eBay (EBAY) subsidiary owns about half of the online-payment industry’s market share, and it doesn’t plan on rolling over. Amazon doesn’t have to take this market by storm right away. The cost is relatively minimal, and incremental, and third-party sellers are going to do the marketing work. In other words, the company has nothing to lose here, and everything to gain. And even a small slice of the market would be a big victory for the value of AMZN stock. The online payment industry is on pace to transact $2.7 trillion worth of commerce next year.