Well, as annoying as it is to have money sitting around and not enough notes to invest in, I think it is important that Lending Club is sticking to their strict loan criteria. I wouldn't want LC to start lowering their standards in order to make more loans available.
Honestly, I think it is a simple supply and demand scenario - as the popularity of P2P lending grows, and more big-money investors come on board, it takes more and more loans to meet that demand. Personally, I don't think enough borrowers are aware of companies like Lending Club and Prosper. For anyone with good credit and a substantial credit card balance, it's a no-brainer to consolidate their debt with a P2P loan, but most people I've talked to haven't heard of this option..... Just my 2 cents worth........