Why Delta Air Lines Inc., Harley-Davidson, Inc., and Facebook, Inc. Are Today's 3 Worst Stocks

The ADP employment report, a much-watched monthly gauge of U.S. private sector employment, walloped Wall Street estimates today. According to ADP, private sector payrolls expanded by 281,000 last month, a far cry from the 213,000 consensus experts had called for. Stocks were blasé about the bullish data, hardly budging from yesterday's levels. Delta Air Lines , Harley-Davidson, , and Facebook, even had the nerve to finish Wednesday deep in the red, as three of the S&P 500 Index's worst decliners. The S&P advanced only slightly, adding 1 point, or 0.1%, to end at 1,974, a record closing high.

With America's birthday looming on Friday, Wednesday marked the last full day of trading in the holiday-shortened week; markets will close at 1 p.m. ET tomorrow. Not wishing to waste any time, Delta Air Lines investors got a healthy dose of selling in today, as shares plunged 5.1%. The airline, which keeps shareholders informed with monthly reports on various metrics, announced some less-than stellar June results today. In particular, the higher-margin international traffic advanced a meager 1.9% last month, a deceleration of more than 50% from April's growth levels.

One thing's for sure: Delta's international struggles in June probably weren't due to droves of Harley-Davidson riders taking to their bikes for intercontinental trips. Aside from the sheer impracticality of a mass, choreographed migration of bikers (Myrtle Beach Bike Week being a notable exception), there's the issue of Harley's second-quarter sales. The stock fell 3.6% on Wednesday after research firm Raymond James downgraded shares to "market perform" from "strong buy," citing channel checks that implied chopper sales at the iconic company probably wouldn't live up to Wall Street's 11% sales growth estimate for the second quarter.

Facebook's own Facebook page encourages users to create groups for those with similar interests. Who's passionate about business ethics? Image Source: Facebook.

While about half a dozen utilities stocks lost more ground than Facebook shares today, their underperformance had more to do with systemic concerns about the sector they hail from than anything company-specific. Facebook stock, meanwhile, lost 2.4% Wednesday under much more interesting -- and controversial circumstances. The world's largest social network admitted to running a psychological experiment back in 2012 on hundreds of thousands of its users -- without their consent. The company only apologized today - and for the way it communicated to users about the experiment, not for actually conducting the experiment itself. The half-hearted apology followed news that Britain had launched an investigation into the experiment, which tested whether manipulating a user's "news feed" would in turn affect the user's own mood. The results confirmed that this was the case.