Bad days. We all have them; some of us deserve them.

Here are five stocks whose naughty ways drew investors' scorn on Monday:

Company

Closing Price

CAPS Rating
(5 max)

%Change

52-Week Range

Myers Industries (NYSE:MYE)

$14.98

**

(30.52%)

$14.93-$22.73

Overstock.com (NASDAQ:OSTK)

$18.74

*

(21.39%)

$14.05-$39.39

Learning Tree (NASDAQ:LTRE)

$21.23

**

(20.55%)

$8.87-$27.71

Celgene (NASDAQ:CELG)

$49.18

****

(14.26%)

$47.21-$75.44

Horizon Lines (NYSE:HRZ)

$17.87

****

(6.54%)

$17.76-$36.55

Sources: The Wall Street Journal, Yahoo! Finance, Motley Fool CAPS.

Naughty?
Well, OK, we can't exactly call these stocks naughty. But none of them gets much love from our 77,000-person-strong Motley Fool CAPS community of amateur and professional stock pickers.

To the contrary -- when it comes to these stocks, CAPS investors have gone thumbs down more often than film critic Roger Ebert. They don't believe any of these stocks are worth owning, and they think some may be worth shorting.

Which of today's candidates is worst? Read on, dear Fool.

Worse
We begin with Learning Tree, which provides continuing education to technology managers. An analyst at Stifel Nicolaus downgraded the stock Monday due to valuation concerns, saying, "We feel valuation is fair, relative to growth prospects, especially in light of pending challenges in restoring overall top-line growth in a period of slowing economic activity."

"Fair" may be too kind. At 62.3 times trailing earnings, Learning Tree trades at a substantial premium to its industry peers, whose average P/E ratio is 42.8.

Worser
Next up is Celgene, whose drug for multiple myeloma, Revlimid, performed poorly when compared to Velcade, a similar drug from Rule Breakers pick Millennium Pharmaceuticals (NASDAQ:MLNM).

Not that Revlimid is bad, mind you. Celgene says that, when combined with the steroid dexamethasone, its treatment achieved an 87% two-year survival rate in patients. Where it fell short was in eliminating traces of the disease. Velcade was far better at this most important measure, known as "complete response rate."

And I do mean far better. According to press reports, Revlimid achieved a 1% and 2% response rate in low- and high-steroid combinations. Velcade combined with melphalan and prednisone, by contrast, achieved a 35% response rate and an 83% survival rate.

Why should you care? Revlimid accounted for 36% of Celgene's 2006 total revenue. With Velcade's results, that revenue may be a lot harder to come by.

Worst
But our winner is Overstock.com, which disappointed investors when CEO Dr. Patrick Byrne said that fourth-quarter gross margins would come under pressure due to aggressive price-cutting.

I'll be honest: At first I thought the sell-off was an overreaction. Gross bookings are up. So is the average deal size. Why would anyone want to sell into good results like that?

And, really, who cares if gross margins take a temporary dip? Peer Amazon (NASDAQ:AMZN) resorts to discounting all the time. The difference here is that, if Bryne's comments are to be believed, Overstock's price cuts won't produce growth where it counts.

Here's why. Byrne told CNBC in an interview that he expects his company to produce $50 to $60 million in cash from operations this quarter. Trouble is, Overstock's cash from operations fell close to the middle of that range a year ago -- $53.5 million.

Big price cuts. Larger deal size. A cash flow range that brackets last year's result. Overstock and its non-growth growth-story ... Monday's worst stock in the CAPS world.

Do you agree? Disagree? Let us know what you think by signing up for CAPS today. It's 100% free to participate.

I'll be back tomorrow with more stock horror stories.

Fool contributor Tim Beyers, who is ranked 8,526 out of more than 76,000 participants in CAPS, hopes that Keith Olbermann doesn't mind the blatant theft of his "Worst Person in the World" segment from Countdown. Remember, Keith, imitation is the sincerest form of flattery.

Tim didn't own shares in any of the companies mentioned in this article at the time of publication. Find Tim's portfolio here and his latest blog commentary here. Amazon is a Stock Advisor pick. Millennium Pharmaceuticals is a Rule Breakers recommendation. The Motley Fool's disclosure policy thinks that cooked spinach is the worst veggie in the world.