Have you heard of Prosper?

SF-based Prosper is the acknowledged leader in peer-to-peer LENDING. Think of it as a cross between ebay and micro-finance, except the loans sometimes go for thousands of dollars. Big loans can also be split among several "lenders". Interest rates are determined through an auction, and borrowers come with a "credit score". It might not replace banks, but it could steal revenue and inject some efficiency into the small business lending space. I love the concept:

... Today the Net is taking the logic of Asian microlending co-ops global. One of the Web's most intriguing trends is the rise of peer-to-peer lending communities such as London-based Zopa Ltd. and San Francisco's Prosper Marketplace Inc. Fifteen-month-old Zopa (www.zopa.com) has attracted 75,000 members. But the most buzz surrounds Prosper, the four-month-old site (www.prosper.com) whose undisclosed number of members have made about 1,500 loans for over $7 million.

Analysts say peer-to-peer lending could become a big deal. Americans make 6.1 million friends-and-family loans, for more than $89 billion each year, says Asheesh Advani, CEO of CircleLending, a Waltham (Mass.) startup that provides billing services for friends-and-family loans. Forrester Research Inc. (FORR ) lumps peer-to-peer lending with "social computing" phenomena such as blogging, podcasting, and wikis that are shaking up industries. The opportunity lies in consumers' mistrust of financial institutions: In Forrester studies, most people believe their banks put their own interests ahead of consumers', and a majority don't think their financial institutions have strong ethics. Their attitude, says Forrester analyst Catherine Graeber: "If we can get this done cheaper between ourselves, what do we need a bank for?"

That said, Prosper and Zopa probably won't have an eBay-like upside. EBay created the first national market for stuff people used to move at garage sales and craft fairs. But capital markets are dominated by big companies that sell a smorgasbord of credit cards, mortgages, and other products to people with virtually any credit profile—and rates finely calibrated to borrowers' credit scores and other data. Fact is, no one knows if borrowers will reliably repay loans from relative strangers. CircleLending says 14% of person-to-person loans go unpaid in the non-Internet world. Zopa says its default rates are a tiny 0.05%; Prosper hasn't broken out default rates.

Then again, peer-to-peer lending isn't a risk that can't be managed. The key is diversification. Loans are typically divided among lenders; a $5,000 loan might be funded by 100 people. Payments are sent directly to Prosper or Zopa, which distribute the money to lenders and report deadbeats to credit agencies or collection firms. Lenders can simply ignore high-risk borrowers; only 2% of Prosper applications from poor-credit customers have been funded, according to SavageNumber.com, an Atlanta Web site that tracks Prosper data. Formal arrangements seem to make people responsible about repayment even without a bank involved. Advani says delinquencies fall to 5% when friends-and-family loans use his firm's billing service.

The result: Loans are cheaper, while lenders can earn more than from other investments. Last month Doug Sophia borrowed $12,500 on Prosper to buy equipment for his new pizzeria in North Myrtle Beach, S.C., at 11.75%; his local finance company wanted 26%. Meanwhile, Frisco (Tex.) lender Dave Elliott, CEO of a small software company by day, says he expects a 13% return on 97 loans. "There aren't many investments that will get you more than 12% without much management," he says. Zopa CEO Richard Duvall says the average Zopa lender makes 7% to 10% after bad debt is written off, twice what top British savings accounts pay.