Agency MBS holders who weren't levered or forced to sell never realized losses during the GFC. There were short term paper losses on some MBS, but it was overwhelmingly on long-duration fixed-rate MBS and incurred by people who held 5+ year duration bonds and had to sell early.

Short-duration floating-rate MBS, like the ones we use, were fine. And since regulations have gotten much stricter as a result of 2008, that was very much a worst-case scenario.

We specifically chose agency MBS because their yield and risk profile fits startup long-term cash needs very well (no credit risk by definition, stable NAV preventing principal risk, consistent premium over money market, and easy but non-instant liquidity). Essentially their safety reduces the need to diversify across bond types. It's also worth pointing out that MBS already are quite diversified, since each one is a pool of thousands of mortgages spread across different locations, borrowers, and property types.

We might offer non-MBS options in the future, if customers ask for it, but we're not there yet.