Whoa! What Just Happened to My Stock?


The Dow Jones Industrial Average struggled to stay above water most of the day on Friday, but it gave up the ghost when it came out that Wal-Mart was suffering from demoralizing month-to-date sales as expiration of the payroll-tax holiday hit the paychecks of consumers hard. But the index clawed its way back higher and ended the day 8 points higher than where it started to close out the week on a positive note.

It wasn't enough, though, to put the Dow in the green for the week, as it still ended down 11 points from the prior period, marking what we've seen a lot from the market these days: apparent fear of moving to the extreme one way or the other.

The three following companies had no concern about the payroll tax. They were getting the job done and recorded strong gains.


% Gain

Millennial Media


Westport Innovations


Best Buy


Now, resist the urge to high-five everyone in the cubicles next to you. Smart investors won't celebrate until they know why their stock surged, because without a fundamental basis for the bounce, these stocks could just as quickly make the return trip down.

On the go
The ubiquity of mobile communication devices has allowed marketing and advertising to them to reach a tipping point, and analysts think Millennial Media will be the initial winner, because there is limited competition at the moment. It has about a six-month head start before significant rivalries from media exchanges develop, and that should begin materializing in its earnings report due out today.

Consider these facts behind the mobile marketing dynamic: Smartphones account for almost half of the 172 million mobile subscriptions in the U.S., the country with the second highest number behind China at 270 million, while global mobile traffic now accounts for 13% all Internet traffic. And this past Christmas saw online shopping establish itself as a real force for retailers, with nearly a quarter of all Black Friday online sales coming from a mobile device.

The critical mass developing behind mobile led analysts at Janney Montgomery Scott to declare 2013 to be an "inflection point in the mobile advertising industry."

Driving innovation higher
Natural gas engine maker Westport Innovations got some good mileage out of takeover chatter on Friday, with manufacturing partner Cummins the most obvious candidate to do so. There's some sense to the rumor, since the two have had a good working relationship for some time, and though Cummins recently decided to strike out on its own to develop natural gas engines, bringing along the experience and technology Westport holds would be likely to advance its efforts greatly.

Still, investors should know better than to trade on speculation. Plenty of rumors turn out to be just that -- rumors -- and nothing ever develops even if they make all the sense in the world. Until something concrete is actually announced, however, you'd be driving blind by jumping in at this point.

Such a deal!
Showrooming, or using big-box retailers as your research department so you can go and buy a product cheaper online later on, may have hit a wall, at least when it comes to Best Buy, the company that epitomized the impact the trend was having on bricks-and-mortar sales. After fumbling for a response to the trend, it seems to have hit its stride this past Christmas by implementing a price-matching policy that kept its prices -- if not its margins -- competitive.

Now, the electronics superstore has determined to keep that policy in place year-round, following in the footsteps of Target, which also adopted the 24/7/365 pricing strategy. Even though the stock is up 42% year to date, Best Buy might still be a good buy for some investors.

Whoa, Nelly!
As the most advanced designer of engines powered by natural gas, Westport Innovations is a small company with a big goal: to lead the world in transitioning away from traditional oil-based fossil fuels in favor of abundant, cheap, and clean natural gas. The company has a price tag large enough to match its ambition and will need to grow revenue quickly to justify sky-high expectations. To help you determine whether Westport Innovations is right for your portfolio, The Motley Fool has just released a brand-new premium report breaking down the company's opportunities, competitive advantages, and risks. To get started, simply click here now for instant access.

The article Whoa! What Just Happened to My Stock? originally appeared on Fool.com.

Fool contributor Rich Duprey has no position in any stocks mentioned. The Motley Fool recommends and owns shares of Cummins and Westport Innovations. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.

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