At The Motley Fool, we poke plenty of fun at Wall Street analysts and their endless cycle of upgrades, downgrades, and "initiating coverage at neutral." While the pinstripe-and-wingtip crowd is entitled to its opinions, we've got some pretty sharp stock pickers down here on Main Street, too. (And we're not always impressed with how Wall Street does its job.)

Given this, perhaps we shouldn't be giving virtual ink to "news" of analyst upgrades and downgrades. And we wouldn't -- if that were all we were doing. Fortunately, in "This Just In," we don't simply tell you what the analysts said. We also show you whether they know what they're talking about.

Today, we examine three high-profile ratings moves on Wall Street, as our favorite investment bankers position themselves for a new year with new ratings on DepoMed (NYSE: DEPO), EXACT Sciences (Nasdaq: EXAS), and Amylin Pharmaceuticals (Nasdaq: AMLN).

New rating: Market outperform
Citing "encouraging" sales of the company's new Gralise pain medication, JMP Securities initiated coverage of DepoMed with a "market outperform" rating (essentially, a buy rating). The drug has only been on the market a few months, but JMP sees it reaching perhaps $200 million in annual sales by 2018. Even better, now that Abbott (NYSE: ABT) has terminated its licensing agreement as it prepares to split itself in two, the drug is all DepoMed's to profit from.

JMP sees this and other revenue streams lifting DepoMed to perhaps $8 a share within a year, and I can't say I disagree. The stock costs barely two times annual sales today, which is a discount to the P/S ratios common even among larger, slower-growing Big Pharma shops like Pfizer or Merck. Tack $200 million or so more onto annual revenues -- that's DepoMed's enterprise value, by the way -- and I could see the stock doubling pretty easily.

EXACT Sciences
New rating: Market outperform
Like DepoMed, JMP's other recommendation last week is a company centered in the life sciences space. Like DepoMed, EXACT Sciences is now rated a "market outperform" by the analyst. But there the similarities end.

Where DepoMed is currently profitable and sells for a low price-to-sales ratio, EXACT Sciences isn't... and doesn't. In fact, this specialist in colorectal cancer screening costs something on the order of 90 times sales. While it's got a product undergoing phase 3 testing for the FDA right now, there's no guarantee that will pan out, or produce the significant revenue investors may expect. What's more, going from product to market... to profit... may take longer than anyone thinks. At last report, EXACT Sciences had $75 million in the bank -- enough cash to keep its doors open for three years at the current $25 million cash-burn rate. Yet last month, EXACT felt the need to raise $27 million more through a follow-on stock offering.

I won't say JMP is wrong to recommend it, but this latest development doesn't EXACT-ly sound encouraging.

Amylin Pharmaceuticals
New rating: Market underperform
Speaking of discouraging news, the analysts at Rodman & Renshaw recently downgraded shares of Amylin Pharma. Arguing that Eli Lilly's (NYSE: LLY) termination of a development agreement with the company "places a heavy financial burden" on Amylin, the analyst counsels investors to sell the stock.

As Fool biotech ace Brian Orelli described last year, the breakup between Lilly and Amylin leaves the latter with all the potential if its new Bydureon drug pans out, but at a steep cost -- about $1.45 billion in upfront and royalty payments. That's a tough burden to bear, considering Amylin today generates only about $17 million in annual free cash flow. Brian thinks the pros outweigh the cons here, but as Rodman's downgrade shows, at least some "pros" disagree.

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Fool contributor Rich Smith does not own shares of, nor is he short, any company mentioned above. He does, however, have public recommendations available on 57 other companies. Check them out on Motley Fool CAPS page, where he goes by the handle "TMFDitty" -- and is currently ranked No. 333 out of more than 180,000 CAPS members.

The Motley Fool owns shares of Abbott Laboratories. Motley Fool newsletter services have recommended buying shares of Abbott Laboratories and Pfizer. Try any of our Foolish newsletter services free for 30 days. We Fools may not 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.