Does Idle Cash Matter?

There has been constant griping about idle cash not earning interest on Prosper. I had always assumed that the effect was small and that Prosper had better things to be doing with their time. Like fixing collections. I had never bothered to calculate it out. j9359 did and proved that it doesn't matter too much:

For my account the difference is minimal, one or two basis points once past the initial period. But I don't put a whole lot of cash into Prosper and then let it sit idle.

That's right. If there was interests on his idle cash, it'd increase his ROI 0.02%. I can understand why Prosper is trying to improve the pool of borrowers, improve collections, implement a secondary market, enhance statistical reporting tools, or just about anything else ahead of getting interest on idle cash.