Is this meant as a sarcastic humor post? 401Ks, almost exclusively, are invested in the company stock. People have no control over their investment (the matching part, anyway), and they don't completely understand that.
I worked for a division of Rockwell which was sold to Boeing. When they sold the division they didn't allow any of the employees to cash out their Rockwell stock. A friend of mind saw $100,000 evaporate within a matter of months from his nest egg which he had been co-investing with the company in a 401K for over 25 years. All of a sudden, his retirement funds were invested in a company he didn't even work for anymore, and he couldn't sell the stock even if he wanted to! (BTW, the company said this was all legal)
The bottom line is: any money you don't have complete control over does not belong to you.
All the 401k's I've had or seen have a choice of investments, generally stock, bond and money market funds. Yes, the matching part is in company stock -- but hey, that's okay, after all it is a bonus.
And if your friend wanted to protect his own profits in a 401k after a takover he had only to quit the company and rollover or rollout the 401k funds, company stock included. Given the value of some 401k's -- quitting can be the least risk option.
Let's get back to the point I made. Any pensions that aren't carriable -- able to be taken with you -- act as traps when you have to make a moral or ethical decision to leave an outfit.