Fortune has rolled out its annual list of the world's most admired companies. There aren't any big surprises among the top five -- four of them made last year's top five -- yet even the winners in this year's roundup are staring down some big challenges in 2009.

1. Apple (NASDAQ:AAPL) may lose some serious style points if Steve Jobs doesn't come back.

2. Berkshire Hathaway (NYSE:BRK-A) (NYSE:BRK-B) just posted its worst annual loss since Warren Buffett arrived 44 years ago.

3. Toyota is in one of the most banged-up sectors out there, with little hope for automakers to celebrate in the near term.

4. Google's (NASDAQ:GOOG) normally heady revenue growth decelerated to just 18% this past quarter. That's not too shabby, but the ad market is weakening in 2009.

5. Johnson & Johnson's (NYSE:JNJ) marketing practices are stirring up the wrath of the Department of Justice.

Then again, victory on a ranked list is always relative. Apple and Google are still growing. Meanwhile, Buffett's company shed nearly 10% of its book value last year, but when you compare that to the 37% decline in the S&P 500, this has been Berkshire Hathaway's best year relative to the market since 2002.

Still, investors in these top dogs shouldn't necessarily be sitting comfortably. Apple took over the top spot on Fortune's list two years ago, by unseating General Electric (NYSE:GE) -- the same GE that just slashed its dividend last week for the first time in 71 years. GE spent two years on top of the list, after bumping off Dell (NASDAQ:DELL).

So if Apple is following GE and Dell, does this make the magazine's annual list a jinxed honor, along the lines of being on the cover of Sports Illustrated or Madden video games?

Tread carefully, Apple.

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