While the S&P 500 Index (SNPINDEX:^GSPC) may not be setting new all-time records every day, you'd be wrong to assume it's not in the midst of an impressive run of its own. On the heels of unemployment numbers better than analysts even considered possible, the S&P rose 6.9 points, or nearly 0.5%, to close at 1,551. But, even as jobless figures sit at four-year lows, and the benchmark has closed higher in nine of the last 10 weeks, a handful of companies figured out how to lose upwards of 2% today.

The first, most egregious offender was insurance mainstay Aflac (NYSE:AFL), which lost 2.8% today. On Thursday, Zacks Equity Research gave the stock a rank of #5, which sounds like a great rating, but in fact, translates to "strong sell" in the Zacks methodology. The company has had to retool its signature Aflac duck a bit since firing its human mouthpiece, Gilbert Gottfried, two years ago, after he made tasteless jokes about the Japanese earthquake. With Japan making up 77% of Aflac's revenue last year, things would be a lot worse for the company if they'd kept the comic.

Oil refining and marketing company Valero Energy (NYSE:VLO) slipped 2.2% today, as total U.S. output slipped by 3,000 barrels a day the week ended March 1. Valero said it would be moving some of its operations to refineries on the West Coast, as gas rigs are becoming more and more scarce. The switch to more efficient, and innovative technologies can be time-consuming and expensive.

Network and communications company Juniper Networks (NYSE:JNPR) fell 2% today as Wall Street sold off the stock a day after a sudden 5% gain on Thursday. The jump came when shares of peer Ciena shot up 17% after reporting a quarter where margins increased, and losses declined. Excluding certain items, Ciena even posted a small profit, which could be good news for the health of the industry, and similar companies like Juniper.

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