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

Feb. 7

Weekly Loss

Overstock.com (NASDAQ:OSTK)

$21.06

25%

ADT (NYSE:ADT)

$30.04

23%

Mattel (NASDAQ:MAT)

$37.84

12%

Geron (NASDAQ:GERN)

$5.02

11%

Tile Shop Holdings (NASDAQ:TTS)

$14.13

10%

Source: Barron's.

Let's start with Overstock.com. The online discounter took a hit after posting disappointing quarterly results. Revenue rose 16% during the holiday quarter, but a spike in sales and marketing costs squeezed margins to the point where the e-tailer barely broke even. Overstock's adjusted profit of $0.04 a share for the quarter was well short of the $0.52 a share it earned a year earlier as its operating profit took a big hit.

ADT investors hit the panic button after the company delivered uninspiring financials. The provider of alarm-monitoring services missed Wall Street's profit target, earning just $0.43 a share when analysts were holding out for net income of $0.47. ADT has beaten Wall Street profit expectations only once over the past year, so the miss isn't exactly a surprise.

Mattel put away its toys after the playthings maker posted alarming quarterly results. The shocking number was a 13% plunge in Barbie sales. Traditional toys have been a hard sell for parents with kids embracing electronics and digitally downloaded diversions, but at least Mattel's American Girl product line is still growing. 

Geron took a hit after pricing a secondary offering. The biotech sold 22.5 million shares at $4. The move will give Geron nearly $90 million, but the market hates the dilution. It's hard to justify raising money at $4 a share when the stock began the week at $5.62 after soaring nearly 25% a week earlier.

Tile Shop Holdings finally had an independent investigator clear accusations of financial misstatements, but the tile retailer still owned up to some things that should have been disclosed. Usually stocks bounce back after putting things like this in the past, but investors still weren't swayed in this particular case.

Rick Munarriz has no position in any stocks mentioned. The Motley Fool recommends and owns shares of Mattel and Tile Shop Holdings. 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.