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.

Company

Nov. 25 Weekly Loss My Watchlist
Frontline (NYSE: FRO) $2.76 (53%) Add
Groupon (Nasdaq: GRPN) $16.75 (36%) Add
Focus Media (Nasdaq: FMCN) $17.70 (31%) Add
Diamond Foods (Nasdaq: DMND) $27.04 (25%) Add
SIGA (Nasdaq: SIGA) $1.91 (24%) Add

Source: Barron's.

Frontline shed more than half of its value after a Financial Times article indicated that the oil tanker may have no choice but to breach its debt covenants early next year. Frontline rivals Overseas Shipholding Group (NYSE: OSG) and Ship Finance International (NYSE: SFL) shed a little more than 30% apiece on the news.

Groupon is now officially a busted IPO, free-falling through its $20 IPO price. There were plenty of naysayers when the daily deals leader went public earlier this month. A lack of profitability and a competitive market will ding you every time.

Focus Media lost its focus after the Chinese advertising network was slammed in a report by noted short-seller Muddy Waters. The bearish note accuses Focus Media of overstating the size of its fleet of LCD monitors where it blasts televised content and marketing material in well-trafficked areas. Muddy Waters also feels that Focus Media has been overpaying for acquisitions to cover up its fiscal shortcomings.

Diamond Foods was roughed up after it was revealed that the death of an audit committee member was apparently a suicide. The company was already investigating its accounting at the time of his death.

Shares of SIGA hit a three-year low on Friday. The biodefense company posted dreadful quarterly results earlier this month, as revenue fell sharply and its operating deficit widened substantially.

It was a rough week for these five stocks. Let's see if they bounce back.

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Longtime Fool contributor Rick Munarriz calls them as he sees them. He does not own shares in any of the stocks in this story. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.