Chinese Twitter, Sina Weibo, did something very smart: it integrated Alibaba's e-commerce capabilities into its service. Imagine Twitter where you could buy anything you wanted with a click, and you get the idea. "Weibo Payment" is that click, and it connects users Alibaba accounts (called Alipay) with their Weibo accounts. It's as if Twitter and PayPay banded up and allowed us to buy whatever we want in our Twitter streat. Why on earth Twitter hasn't already done this, beats me.
My guess is that Google, once it figured out that it hasn't exactly figured out demands of the retail market (remember Google boutiques?) decided to get into retail delivery. It's a great way to be first in the same-day delivery market and to create both customer- and retailer-lock in via its monumental data services. Once switching costs become too high, Google can monopolize the demand and expand its delivery market. It's not a bad idea, even if at the first sight it seems as an unlikely one for the Google brand.