Sprint's got a nice head start in the 4G race over Verizon and AT&T -- a message it's heavily broadcasting these days -- but with the onslaught of LTE networks and equipment around the world now just months away, momentum is unquestionably going to shift, giving the carrier every reason to act quickly to build out now and score as many subscribers as it possibly can. That seems to be the gist of a rumor coming out of AndroidGuys today that says Sprint is working on a deal with Walmart to install WiMAX cells on all (yes, all) of its locations, a move that would give it a significant boost in national coverage while presumably lowering infrastructure costs significantly. As many Walmarts as there are, it seems like this would still leave huge coverage gaps (particularly in rural areas) between locations, but hey -- maybe these guys are going for the parking lot RV crowd, which would actually make a ton of sense. Best part? You'd probably be able to buy the modem right in the store.