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.


May 17

Weekly Loss

Oncothyreon (NASDAQ: ONTY)



Cliffs Natural Resources (NYSE:CLF)



Molycorp (NYSE: MCP)



Taseko Mines (NYSEMKT:TGB)






Source: Barron's.

Let's start with Oncothyreon, which took a hit after offering uninspiring clinical data for Stimuvax. The biotech and its investors had big hopes for the experimental lung-cancer treatment, but its latest study didn't meet Oncothyreon's goal of materially improving the overall survival rate.

Cliffs Natural Resources saw its shares soar 18% a week earlier after receiving a timely FBR Capital analyst upgrade, but this week the iron ore miner resumed its losing ways. Fears of diminishing demand -- particularly as China's once smoking-hot economy slows -- are weighing on the shares. The stock has shed nearly half of its value in 2013.

Molycorp tumbled on a week that slammed most commodity stocks. The volatile rare-earth minerals miner had moved sharply higher earlier this month after delivering a much smaller quarterly deficit than analysts were expecting, but Molycorp joined other mineral miners on the way down this week.

Taseko Mines slipped earlier this month after posting a quarterly loss and announcing that its CFO was leaving. This week's slide was related to the continuing slump in metal prices, and a move on Friday to initiate a shareholder-rights plan did little to lift the shares of the Canadian copper miner.

Velti fell after the Dublin-based mobile marketing services provider posted disappointing quarterly results. Revenue fell 21% in the latest quarter. Wall Street knew it was going to be a bad quarter. Velti had let go a fifth of its staff earlier this year, bracing for a slowdown. However, Velti's guidance wasn't very encouraging.

Ready for a bounce
If you owned some of these losers, how about following the smart money into winners?

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.