5 portfolio time bombs

Stocks can be scary, but a portfolio that's too conservative carries a far greater risk: that you won't have enough money for retirement.

Assuming typical historical stock and bond returns, a $200,000 portfolio with 25 percent in stocks and 75 percent in bonds will be worth $500,000 less after 25 years than one with these positions reversed.

Still, many investors remain skittish about equities: According to the Employee Benefit Research Institute, almost a quarter of 40-year-olds have 60 percent or more of their money in bonds and cash; 19 percent of twentysomethings own no stocks.