Stocks go up, stocks go down -- and so do analysts' opinions of them. This series, brought to you by Yahoo! Finance, looks at which upgrades and downgrades make sense and which ones investors should act on.

Today, we're taking a look at new ratings for Nike (NYSE: NKE), Nokia (NYSE: NOK), and for a change of pace, one company that doesn't start with the letter "N" -- Best Buy (NYSE: BBY). Let's dive right in.

Nike no longer a laggard?
First up, Nike. The world's most famous footwear maker took a bit of a tumble yesterday, tripped up by reports that one of its star endorsers, cyclist and cancer survivor Lance Armstrong, is now under investigation for alleged "doping" violations. But the stock's one-day, 5% pullback has one analyst thinking the damage is overdone. This morning, Seattle-based regional broker McAdams Wright Ragen announced it was removing its sell rating on the stock, and upgrading to hold.

And to an extent, McAdams is right to do so. After all, the allegations against Armstrong are so far just that -- only allegations. And allegations that Armstrong rejects as "baseless, motivated by spite and advanced through testimony bought and paid for by promises of anonymity and immunity."

Problem is, Armstrong isn't Nike's only problem. There's also the stock price to consider, which at 21 times earnings, seems a mite pricey relative to long-term expectations of 13% profits growth at Nike. In short, McAdams may be right that the Armstrong kerfuffle is an overreaction, but that doesn't make Nike a buy.

Oh, no, Nokia!
And speaking of stocks you should not buy, Finnish cellphone specialist Nokia just got hit with a downgrade to "underperform," courtesy of the analysts at Robert W. Baird. No surprise here, considering the news Nokia released last night:

  • 10,000 new layoffs (20% of the company's workforce).
  • Continued market share losses to iPhone and Android.
  • $1.25 billion in new restructuring charges.
  • And on, and on, and on.

While Nokia's new Lumia line of smartphones continues to garner praise, the company that makes the phones has become Wall Street's whipping boy. Sadly for shareholders, until Nokia proves itself to be anything other than another Research In Motion, it probably deserves the criticism and the "sell" rating, too.

"Best" Buy? Not exactly, but...
On the other hand, sometimes it really is darkest before the dawn. If there's any company out there that's had more bad press than Nokia (and the question really is debatable), it's almost certainly Best Buy. Dogged by free-shipping, sales-tax-free competition from Amazon.com (Nasdaq: AMZN), Best Buy and its fellow big-box stores have largely been reduced to "showrooming" goods that consumers ultimately buy online. This has many pundits busy writing obituaries for the business, and advising that investors sell the stock.

Many, but not all. This morning, Citigroup announced it was pulling its "sell" rating on Best Buy stock, and upgrading Best Buy to neutral with a $21 price target. The reason is simply that a stock can only fall so far, and Best Buy may be reaching that limit. With shares priced at 5.3 times earnings, a dividend yield of 3.2%, and even the most pessimistic analysts admitting Best Buy is still capable of mid-single-digit growth -- Amazon or no Amazon -- Citi may be right.

Best Buy may not be the literal "best" place to put your money. But with the bad news largely priced into its battered shares already, the downside is now limited. As for whether there's any upside here, well, make sure to tune back in in August, when Best Buy reports its Q2 earnings.

Fool contributor Rich Smith owns shares of Nokia, but he holds no other position in any company mentioned. The Motley Fool owns shares of Amazon.com and Best Buy. Motley Fool newsletter services have recommended buying shares of Amazon.com and Nike. Motley Fool newsletter services have recommended creating a diagonal call position in Nike.