Ever since Thursday's news that Oracle was naming not one but two people to replace Larry Ellison as CEO, many commentators have pointed to the conventional wisdom that a co-CEO arrangement rarely works. It can be confusing. It sets up a "funky dynamic" for executives who've typically long wanted the top job. It's "another case of excess" for one of the corporate world's highest-paid gazillionaires.

And certainly, there's little question the setup comes with some serious risks. Both people have to share the same vision. Egos can get in the way, decision-making can slow down and lines of accountability can be harder to draw. Shareholders might balk at the cost — a potential issue at Oracle, where both Mark Hurd and Safra Catz, the company's newly named CEO duo, were each making far more than the median public company CEO even before their appointments.

Those are just a few of the reasons that boardroom history is littered with CEO duos that didn't ultimately pan out at big companies: Martha Stewart Living Omnimedia, Wipro, Citigroup, SAP.

But let's not be too quick to say this set-up is doomed. Unlike many past co-CEO flops, Hurd and Catz have been working side by side in equal-level jobs since 2010. They already know where the boundary lines are drawn, how the other person can help and when's the best time to back off. As Adam Lashinsky wrote in Fortune, the two were expected to clash when Hurd first came to Oracle, but those predictions have been wrong. Instead, "they appear to have quickly carved up their respective turfs and then run them ruthlessly." 

That should help them. Research has shown that the co-CEO setup can be effective if the two leaders have highly complementary skill sets. It's a potential advantage in a world where the job of a multinational CEO is so extraordinarily complex. That appears to be the case with Hurd and Catz. Catz is the behind-the-scenes operator, known for her prowess at dealmaking; her oversight of manufacturing, legal and finance; and her longtime role as Ellison's consigliere.

Hurd, meanwhile, is the external face of the company, regarded for his command over Oracle's sales, his relationships with important customers in the form of chief information officers, and his data-driven execution skills, which won him plaudits as Hewlett Packard's CEO before a scandal prompted his departure. The combination of their divergent skill sets could be a real asset at the top.

Finally, let's not forget Ellison isn't exactly disappearing.

One of the chief complaints about the co-CEO model is that it can slow things down and leave no one ultimately in charge. To succeed, recent research has shown, one of the two CEOs needs to be the de facto decision maker. It could be that dynamic is already figured out between Hurd and Catz, and they just haven't revealed it to the world. Or it could be that when they don't agree on something, Ellison will help cast a deciding vote. He's not retiring to his yacht just yet, after all. As a founder who owns 25 percent of the stock and will remain both executive chairman and chief technology officer, Ellison will still be very much a part of the management team.

In fact, in a conference call with analysts, the three insisted nothing was substantively changing due to the title shift. "There will actually be no changes," Catz told analysts. "No changes whatsoever." 

How much that's a good thing or a bad thing is a big question, though. That "no changes" philosophy may not reassure investors who were worried after Oracle missed its fourth quarter profit expectations back in June. And if Ellison steps in too much, that could be challenging more than it is helpful. It's difficult for any new CEO who has to follow a founder, much less one who's sharing the arrangement with another CEO.

My guess is that this is the biggest risk factor. If the co-CEO arrangement between Catz and Hurd fails, it won't simply be because they're sharing the job with each other, but because they're also sharing power with an iconic founder who remains very much involved.

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