I experimented with Lending Club, lending a small amount of money in early 2008. (Nice timing right - the recession was December 2007 to June 2009.) I have a few loans still outstanding, but most have prepaid or defaulted by now. I did not reinvest as payments came in.
Based on my experience, one "catch" is lack of liquidity. It's like buying individual bonds rather than a mutual fund.
Your money is NOT just tied up for the 3-year loan term, because to get good returns you have to keep reinvesting as people pay off their loans. So you always have some just-reinvested money with the full 3 year term left, and that's how long it would take to get all your money back out. You can't just cash out when you feel like it.
They have a trading platform (which I did not try out) if you want your money sooner, but I would guess the spreads are wide and you have to take a hit when you sell loans. Again though I did not try the trading platform.
On the upside, the yields did seem fine. I got 19 eventual defaults from 81 loans, but many of the borrowers made a number of payments before defaulting so only part of the money was lost. The lower credit ratings default more often obviously, only one of 19 defaults had the top credit score. (I tried investing across a range of credit ratings.) The interest rates appear to cover the risk of default, at least on average. You can of course have varying luck.
I made only a slight profit over the 3 years, but I did not reinvest after the first couple months, and it was during a recession. So the claimed yields look plausible to me if you reinvest.
They do get people's credit scores, report nonpayment on people's credit reports, and even send people to collections. Seems like borrowers have a reason to pay the bill. In 2008 I think this was a difference compared to the other peer lending sites, but I don't know if that's still true.
Anyway, for what it's worth the site seemed to work fine and "as advertised" for me. I probably will not invest more money there for a couple reasons:
- the liquidity issue
- I feel like I'd have to do more due diligence and research, and I don't have time
- I moved to a state where they only allow trading, not new loans
However as best I could tell from my experiment, it is a perfectly reasonable place to put a portion of your portfolio you might otherwise invest in something like high-yield bonds or some other sub-investment-grade fixed income.
Update: here's a useful NY Times article: http://www.nytimes.com/2011/02/05/your-money/05money.html