Subject: Re: NOT OT: GUNDLACH
Just a reminder, the vanguard federal mmf currently yields 4.6.'

This is easier:
VGSH Vanguard Short-Term Treasury ETF
30 day SEC yield 4.73%

It may be easier, but it's not the same.

When investing in bonds you need to pay attention to both credit risk and duration risk.

Obviously there is no credit risk in both, but VGSH has a duration of 1.9 years whereas Federal Money Market Funds have a duration of 7 days.

Duration risk, also known as interest rate risk, is a measure of the effect on price changing interest rates will have. This can work for or against you depending on which way interest rates are going.

If the goal is to have cash which is earning some interest, a Federal Money Market Fund is absolutely the way to go.