The Wall Street Journal this morning explains how a consortium of retailers is working together to launch their own mobile payment system. The group includes heavyweights such as Wal-Mart and Target, so it looks to be a force to be reckoned with as it tries to compete with a host of services including Google Wallet, PayPal Mobile and the carrier-backed Isis. But there simply isn’t room for many different systems in this space — I don’t think consumers will embrace more than two, and maybe only one — and the competing services will only shackle the market. So this new effort will likely slow uptake of mobile payments rather than spur it.