BillMonk's initial service, a hybrid of social networking and personal finance, offers the ability to track (via the website or using mobile phone SMS) what the founders call "social money" - informal debts between friends and family.
With respect to the company's business model, this comment from a recent BillMonk blog post provides some insight into how BillMonk intends to make money:
One advantage of informal debts is that you can use a past debt as an informal currency for a future purchase. For example, my girlfriend owes me $100 for a deposit on a ski cabin; since then, she’s been picking up all our restaurant tabs and has beat down the debt to $30.Learn more about BillMonk here and on the company's blog.
That said - and this answers a key point of John’s article, about how we’ll make money - we fullly intend to collaborate with financial institutions to offer our users the ability to settle up with cash when they see fit. If the social money market is as big as we think, this offers a great business opportunity for us and our partner institutions.