In entrepreneurial companies, corporate culture--that amorphous yet defining sense of who we are, how we act, and what we believe--is shaped chiefly by the character of the founder. One reason management transplants often fail is that the new CEO fits her adopted culture as poorly as a Park Avenue matron set atop a trailer-park brood on the program Trading Spouses.

Not surprisingly, charismatic founders touting hard-held beliefs have no trouble creating businesses in their own images. Larry Ellison begat a tough-bastard company; Ben Cohen and Jerry Greenfield begat a cuddly one. But some entrepreneurs aren't very dynamic. (Not many of course. And not any of you, dear readers.) These not born leaders may be introspective, or uninspiring, or may communicate poorly. Lacking discernible passions or even strong preferences, they leave little imprint on their followers. Employees in companies with dynamic leaders guide their behavior by asking: What would Wally do? Employees in companies with nondescript leaders barely recall who Wally is.

Some founders may not care if their businesses don't resemble them. But companies can't help but develop personalities over time. And here's where the Limburger-in-the-icebox principle comes in. Foods in the refrigerator absorb the odors of whichever of their shelf companions is most fragrant. Similarly, companies not branded by their creators sometimes assume the personalities of their most dynamic, personable, or just plain loud denizens. Without attention from the CEO, a company's culture is at the mercy of the human equivalent of stinky cheese.

There are obvious reasons not to let an employee--even unintentionally--hijack your culture. For example, the strongest personality in the business may be some jerk you brought in to make rain. Sure, he plays symphonies with your top line, but the idea of others imitating his arrogance and frat-boy manners makes you shudder. Or he may be someone whose values differ from yours--although other employees won't recognize this because you have failed to make your values clear. I knew one entrepreneur--personally very cautious about investing in new ideas--who spent most of his time out of the office (another way CEOs sacrifice influence). In the leader's absence, an eloquent advocate of innovation-or-bust captured the imaginations of the staff.

In some cases your company's dominant personality may be a model of integrity and charm, and employees' affection for her a testament to their good taste. Still, staff loyalty is precious; you can't afford to let it stray. If the company's de facto heart and soul quits for any reason, morale will plummet--and guess who will be blamed. And if, heaven forfend, she leaves to start her own business, expect to see your best people pied-pipered out of the building.

Leaders can be many things: benevolent, dictatorial, funny, hip, hypercompetitive, brilliant--even charmingly nerdy. The one thing they can't be is invisible. Don't leave your company culture to default.

Leigh Buchanan is an Inc. editor-at-large. She can be reached at