[oldcomputerguy]

"Yes of course because every IRA and 401K allows shorting and trading on margin."

No, but they have MM accounts that serve much the same purpose.
I will admit that 401ks are best moved to IRAs as soon as possible and in all cases of job changes. Shorting in IRAs however is quite easy, there a number of bear market funds that work quite well.

[x5452]

Why use funds to do it? It fractions your gains. Grab an account and short it yourself, with money you can afford to be wrong with. Invest the rest in Gold, or diversified currencies.