From the introduction:
Economically Squeezed Families Are Turning to Their 401(k)s to Make Ends Meet
Imagine that you or someone in your family who relied on you for financial help were faced with unexpected medical bills that you could not afford with your current income. Luckily, you have managed to save a nest egg for retirement through your 401(k) plan, the most common defined-contribution retirement savings plan in the United States today, and you can simply borrow against that to keep the bill collectors at bay. Since the money is yours, there is no approval. You may borrow up to half of your retirement savings with no penalty so long as you pay it back within 5 years. Even better, the interest rate on these borrowed funds is lower than those on many other loans.