Here are five examples of how the year after the meltdown changed old thinking about investing:
Conventional wisdom: Safe investing means adjusting the mix of stocks and bonds in a portfolio based on an investor's age and appetite for risk. Younger investors were advised to own more growth stocks, then transition as they aged into more shares of well-established, blue-chip companies and into bonds, which return less but are less risky. Stocks were expected to beat bonds handily over the long haul.
New thinking: Going back five years, to well before the recession, bonds win. You have to measure back 20 years to find a long-term edge for stocks, and even then it is small.
"It's definitely blown up the view that stocks always outperform over long periods," said Tony Rodriguez, head of fixed-income strategy at First American Funds in Minneapolis.
But bonds also may face headwinds in a few years. Deficit spending by the federal government may ignite inflation and drive interest rates higher, which would depress the price of bonds.
"Bonds are about to take a big hit," said Dan Deighan of Deighan Financial Advisors Inc., a firm in Melbourne, Fla., that manages more than $150 million for wealthy investors.
Conventional wisdom: You should diversify your stock portfolio to protect yourself in bear markets and get the best returns in bull markets. In downturns, count heavily on "value" stocks - those considered cheap compared with historically steady earnings. To take advantage of good times, own more volatile "growth" stocks - those expected to have rapidly growing earnings.
New thinking: The dramatic stock rally since March suggests a slowdown is inevitable and that it is time to move more into value stocks. But it all depends on what type of economy emerges. Typically, the economy will grow at least for several years after a recession. But this time, Americans are hesitant to spend because of the high unemployment rate and the lasting effects of the housing bust.
A slow economic recovery could send the market into a "W" pattern - big gains followed by a second steep decline.
Experts say we should expect more volatility in the economy - a choppy recovery, not a steady upward climb. That makes any broad bets about which types of stocks that will gain the most in coming months and years an unusually dicey proposition.
Conventional wisdom: Keep stocks and bonds as the foundation of your portfolio and put minimal amounts in other types of assets.
New thinking: Put more of your retirement nest egg in tangible assets. Think about real estate other than your home, as well as gold bullion, says Deighan, the Florida financial adviser.
Many investors have already turned to gold and real estate as hedges against stock market downturns, higher inflation, and a weakening U.S. dollar. Real estate prices in much of the country are perceived as having hit bottom. Gold had a great run over the last year - from about $700 an ounce a year ago to more than $1,100 now.
Conventional wisdom: Stocks that pay dividends ensure you a steady stream of income.
New thinking: To conserve cash, companies have been cutting dividends at a record pace. During the five decades before last fall's meltdown, about 15 companies increased their dividends for every one that cut, according to S&P. This year, dividend cuts are running ahead of increases.
Companies cut dividends because they need to conserve cash. And once a company cuts, it often does not restore its dividend to its previous level until it is confident it can afford to give up the cash. And that can take years.
Georgia resident Elaine Durham Mobley, 75, a retired bank accountant, has lost about a third of her $64,000 annual income to dividend cuts. "I always thought these dividend stocks were quite safe," she said. "But we have to remember the law: There's nothing sure in life but taxes and death."
Conventional wisdom: Some investments are risk-free. You can put money in them and not worry whether it is safe.
New thinking: There is no such thing as risk-free. At the height of the financial crisis, one large money market mutual fund, the Reserve Primary Fund, exposed investors to losses because the fund bought debt of Lehman Bros. Holdings Inc., which went bankrupt. It was just the second instance of a money fund "breaking the buck," or falling below $1 a share, in the last four decades.
The government rushed in with guarantees for money funds similar to banks' FDIC insurance - guarantees that expired in September. New rules will further restrict the investments money funds can make and lower their risk. But they come at a cost. Money funds are averaging yields of less than one-tenth of 1 percent - barely better than cash.