I realize this isn't to the point of the question (of course you can buy bonds, etc., in a 401k).
But I seriously cannot fathom people wanting to jump OUT of stocks right now unless you need that money in the next 3 or 4 years. I was forced by circumstances to pull back investment during 2008 and it made me insane with rage. We'd be at least 100K ahead right now if I could have just stayed the course during the drop, let alone INCREASED buying, which was impossible.
But it's possible now!
I just set up a 90/10 s/b ratio index fund Roth and maxed it in the first 2 months. I started a Roth for my husband and set it to dollar cost average. Now I'm about to set up a 90/10 s/b ratio i401k and start pouring every spare dollar in.