The web’s still buzzing about a story the Wall Street Journal broke yesterday on a potential Google e-commerce initiative. Reportedly, Google is trying out an idea on major retailers that would tie together various components of its own offerings and theirs, and use third-party overnight mailing to re-create an Amazon Prime-like one-day shipping service. It sounds like a trial balloon to me, and sources tell the New York Times anything that happened would occur initially in a very limited trial, perhaps in a couple of big cities like San Francisco and New York. It’s an intriguing concept – no need for Google to build warehouses, because it could coordinate shipping from local inventory in stores. And maybe there’s a role for Google’s Wallet, and Offers, at some point. But lots of customers expect free shipping, and an offering like Prime is no good without a critical mass of availability and products. Google is trying hard to make its Product Search more useful, but meanwhile it can add to its core ad network business without such grand schemes.