My understanding is that the rolling market works very much as you detailed.Ratesetter don't make any secret of that risk attached to withdrawal from the rolling market though:"Access: You can access your money freely as long as there are funds in the market to replace the amount being withdrawn. This could come from money already rolling in the market, new investors or funds set aside by RateSetter. If replacement funds aren't available, your money will be returned as the borrower(s) repays over their loan term. To date no customer has ever had to wait for their money although it's not a guarantee. RateSetter is an investment not a deposit account."The key part mitigating the risk slightly is "funds set aside by RateSetter" (i.e. RateSetter could theoretically use some of its own income from operations temporarily to plug the gap between your withdrawal and the money from the underlying contract flowing in). I believe there was some recent fuss about them lending out a small part of the Provision Fund, so that (rightly) has been binned, but that still potentially leaves their own investors' money and/or lending fees as potential sources of liquidity.