Time Magazine - Why It's Time to Retire Your 401(k)

Withdrawals from 401(k) plans are now exceeding new contributions as baby boomers are cashing in thus pulling liquidity out of the market. This is going to decrease the value of stocks (401k) and the closer you are to being 15 years out from retiring the greater risk of losing value in your 401k.
To further exasperate the stocks as an investment vehicle the McKinsey Global Institute forecast back in 2008 that this demographic effects could slow the average annual growth rates from about 3.2% to 2.4% over the next three decades thus creating a contraction in the economy. Companies will have less of an incentive in seeking capital regardless of the funding's source. Depending on your age the 401k can indeed be a bad retirement plan. Get diversified.