PayPal, the payments unit of eBay, just dropped a cool $800 million on Braintree, a smaller rival. We hope it’s not done.

As we noted, Braintree will help PayPal boost its appeal to app developers, who have been frustrated with its older software and cumbersome customer-service operations.

But PayPal needs more pieces to really win the battle as e-commerce takes over the physical world.

I think one of those might just be Foursquare, the maker of a popular location check-in app.Checking In To Retail

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