There's never a shortage of losers in the stock market.

Let's take a closer look at five of this past week's biggest sinkers.


Feb. 3 Weekly Loss My Watchlist
MannKind (Nasdaq: MNKD) $2.17 (34%) Add
Hyperdynamics (NYSE: HDY) $240 (29%) Add
RadioShack (NYSE: RSH) $7.39 (27%) Add
ShoreTel (Nasdaq: SHOR) $5.40 (24%) Add
Polypore (NYSE: PPO) $46.83 (17%) Add

Source: Barron's.

MannKind was the market's biggest loser, shedding a little more than a third of its value after announcing a dilutive stock offering. MannKind's run into a few speed bumps -- and apparently now a cash crunch -- in getting its inhaled insulin Afrezza on the market.

Hyperdynamics was the Big Board's biggest decliner. It too announced a dilutive share offering at a healthy market discount, and that was enough to prompt Howard Weil to downgrade shares of the oil explorer.

Small-box retailer RadioShack got even smaller after announcing dreadful preliminary results for the holiday quarter. Thinning gross margins find the consumer electronics chain targeting a profit of no more than $0.13 a share for the holiday quarter, well short of the $0.37 a share that analysts were targeting.

ShoreTel may have posted a surprising quarterly profit, but it was the provider of Web-based telephony's bleak near-term outlook that led to investors hanging up on the stock.

Finally, Polypore took a hit after a former customer revealed plans to compete with the company by building its own plant to make filtration membranes. A couple of analysts downgraded Polypore on the news.

It was a rough week for these five stocks. If you want to shake yesterday's losers and ride tomorrow's winners, a new special report reveals Motley Fool's top stock for 2012. It's free, but only for a limited time, so check it out now.