They bought treasury bills, is that really irresponsible? Of course on Monday morning everyone says they were obviously being dumb not hedging their rate risk, but how many people were saying that before Friday?
You can literally call up your 401k/403b provider tomorrow and ask for the bond fund/portfolios/allocations available. See if you can find any bond fund with no short-dated maturities.
It's equivalent of having a 100% tech stock portfolio and not hedging sector risk. Maybe it isn't as irresponsible as going 100% into a single stock ticker, but it's still extremely irreponsible
SVB reportedly bought longer-duration US Treasury debt which is more sensitive; one source says their portfolio had an average duration of around 5.7 years, up from 4 years a bit over a year ago: http://twitter.com/MacroAlf/status/1634626136364679168
The issue with longer-term debt is that if you need the money now, you can't force the issuer to redeem it before the bond matures - instead, you have to find someone else to buy the bond it from you. And if it's paying half the interest that a new issue would pay, nobody's going to give you face value.
https://www.netinterest.co/p/the-demise-of-silicon-valley-ba...