Burried in the Economist’s recent article on “The frontier of finance” was the little number that M-PESA is about to hit 1 million users signed up for its mobile payments service in Kenya. So what: mobile banking is gathering steam. That’s old news.

But lost in all the buzz is the critical role third-party agents serve in the play for millions of low-income clients. A broad range of corner stores, petrol stations, lottery kiosks, post offices and other outlets feature prominently in the system architecture for such success stories as Safaricom’s M-PESA in Kenya, as well as in other countries, such as Globe Telecom’s GCash service in the Philippines.

Customers can sign-up for an account, deposit and withdraw funds via an agent. In fact, for mobile banking platforms run by mobile operators who don’t have a bank partner, agents may be the only way clients can sign up. No agents: no customer acquisition. And for mass market customers who want easy cash-in/cash-out, agents are the critical bridge from the electronic device to the cash economy they live in.

And finally, for managers having to show sizeable returns within a reasonable investment period, agents contribute to rapid scaling up in customers, transactions and cash-flow.

Consider this: M-PESA is about to hit 1 million registered users in less than 10 months operation. That amounts to a customer base one-third of the size of all of the clients of all of the banks in the country (approx. 3 million Kenyans have a bank account). M-PESA did it by building a network of 850 agent locations, which compares very favorably to the 550 bank branches in total. In the Philippines, GXI and Smart have over 5.5 million customers signed up, accessing service via more than 5000 agent outlets.

No doubt, customer uptake is measured by more than just sign-ups, and usage is a key driver for transaction-based fee revenue. Product design, ease of use on the mobile phone, marketing and other factors affect all this, but agents are a lynchpin in the business model for outfits like Safaricom and Globe aiming banking the unbanked.