While Apple ( AAPL) shined, emerging-market stocks had a bad day Tuesday, thanks largely to Venezuela President Hugo Chavez's plans to nationalize his country's telecom and power industries. But a bad day shouldn't be extrapolated to mean the global economy is suddenly weak, or that risk appetite is waning on a large scale. The plunge in emerging markets reminded many traders of late April and early May 2006, when emerging market stocks sold off ahead of U.S. stocks. Indeed, an emerging market selloff may well be the crack in the rally that gives investors reason to kick off a correction in the U.S. stock market. But it doesn't necessarily foreshadow a weak economy or impending disaster. The iShares MSCI Emerging Markets Index slid 2.3% Tuesday; Brazil's Bovespa fell 2%; Mexico's benchmark IPC Index lost 1.8%; and Venezuela's Caracas Stock Exchange Index fell 30% in 15 minutes of trading. Emerging-market weakness wasn't contained to South America only. The iShares FTSE Xinhua China 25 Index fell 4.3% on the day, while Russia's major index slid 6.4%. Some investors likewise lament the overall decline in commodities lately (though natural gas, heating oil, copper and gold rose Tuesday) as reason to worry about the global economy. Some traders have attributed some of the emerging-market selling to the commodity weakness, and warn of contagion.