NEW YORK (CNN/Money) - Quick question. Do you know who Susan Patrick and James Follo are? Probably not.

With all due respect to the president and chief financial officer of Martha Stewart Living Omnimedia, we'd guess that most of the company's shareholders own the stock because of the formidable presence of CEO Martha Stewart, and not because of the talents of other senior executives.

So what would happen to Martha Stewart Living (MSO: Research, Estimates) without Martha? Although the company denied a New York Times report on Wednesday that it was considering a search for a new CEO in order to detract from her involvement in the ImClone insider trading scandal, it still raises the question: Should investors be wary of companies whose fortunes are heavily tied to one person?

To a certain extent, yes. "If you wind up with a company that is so closely aligned with one individual, like it or not, the virtues of that company are tied to the virtues of that individual," says Robert Zagunis, co-manager of the Jensen fund. "You're usually much better off with CEOs who are under the radar and just work at doing a very nice job for shareholders."

Take Martha Stewart (not literally....this is not the punch line to a Henny Youngman joke). Although the company reported a 16 percent increase in revenues in the second quarter and better-than-expected earnings, the company lowered forecasts for the rest of the year, citing concerns that the insider trading probe will continue to impact business.

Oracle is another good example. Although the company is a profitable industry leader in database software, there have been numerous concerns about who will replace the company's enigmatic co-founder and CEO Larry Ellison -- and that's hurt the stock.

Two high profile executives that were widely believed to be heirs apparent to Ellison left the firm in a span of two months during the summer of 2000. And the lack of a clear-cut successor to the 57 year-old Ellison on the horizon appears to be one reason why Oracle's (ORCL: Research, Estimates) stock has taken a hit along with the rest of the software industry during the past two years -- it's down nearly 80 percent since September 2000.

Oracle isn't the only technology company that has been hurt by management problems at the top. Sun Microsystems nose dived this spring after three senior executives left the company. Although there appears to be no major reason to suspect that CEO Scott McNealy is leaving anytime soon -- he is just 46 -- there is still cause for concern.

McNealy, like Ellison, is brash and outspoken. So the departure of senior managers that had held him in check puts even more of a spotlight on McNealy than before. Sun Microsystems's (SUNW: Research, Estimates) shares were recently trading at $3.69, just 7.6 percent above its 52-week low.

And remember what happened to Apple after co-founder Steve Jobs left in 1985? The company largely struggled until he returned as a consultant in 1996. He was named interim CEO in September, 1997, a job he still holds. Apple (AAPL: Research, Estimates) has lost a bit of its luster lately but the stock is still higher now than it was when he took control for a second time. The Nasdaq on the other hand has given up all its gains since Sept. 1997. Still, Jobs won't be Apple CEO forever --although he finally removed the interim tag in January, 2000.

Another "cult of personality stock", if you will, is Berkshire Hathaway, the firm managed by legendary value investor Warren Buffett. To be sure, Berkshire has many solidly performing businesses in the insurance sector that generate a lot of cash. But the main reason why people buy Berkshire is because it's a way to get a piece of Buffett, arguably the greatest investor of the past fifty years.

At some point, investors need to prepare themselves for a Berkshire (BRK.A: Research, Estimates) without Buffett. He is 71 after all and his right-hand man Charlie Munger is 78.

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Although it's extremely likely that Buffett's successor on the investment side of Berkshire, Lou Simpson, will adhere to his investing philosophy, there's no guarantee that the market will immediately embrace him. Plus, he's 65, so it's not as if he's a viable successor for the long-haul.

Of course, there are certainly examples of companies where larger-than-life CEOs have come and gone and the company has held up nicely, thank you very much. While it's too soon to tell whether General Electric CEO Jeff Immelt will ultimately be held in the same regard as former CEO Jack Welch, so far GE (GE: Research, Estimates) has been able to keep posting solid earnings gains despite the weakness in the economy.

When Wal-Mart CEO Sam Walton passed away in 1992, it seemed difficult to imagine how the retailer could be even more successful. But Wal-Mart (WMT: Research, Estimates) has continued to flourish. It is now the largest company in the world (based on annual revenues for 2001) and a component of the Dow Jones Industrial Average.

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The key to both GE and Wal-Mart's success, though, was that were plenty of capable managers below Welch and Walton that made succession a smooth process. Immelt, for example, was a GE employee since 1982 and head of its medical business for four years before being tapped as Welch's successor in 2000. Meanwhile, Walton stepped down as CEO in 1988 and handpicked his replacement, Wal-Mart long-timer David Glass, who led the company until his retirement in 2000. Another Wal-Mart vet, Lee Scott, succeeded Glass.

But with no clear-cut succession plans in place at Martha Stewart, Oracle or Sun, these "celebrity CEO" stocks are a lot riskier.