It's been a relationship more than 15 years in the making, but Warren Buffett's time at Coca-Cola (NYSE:KO) is ending. No, he's not selling his stock, a lucrative investment he'd not want to give up any time soon. Rather, Buffett won't seek re-election to the company's board of directors.

As Roger Lowenstein details in the excellent Buffett: The Making of an American Capitalist, Buffett's relationship with Coke began shortly after he switched from drinking Pepsi (NYSE:PEP) to Cherry Coke. Though the Oracle of Omaha jests that it was based on his obsession with the beverage, as always with Buffett, it was sound valuation. He began buying shares of the company on the "down low" at a pre-split price of around $10.96 a share, keeping it quiet until legally required to do so, which happens when someone acquires more than 5% of a company.

After it was revealed that Buffett was a major shareholder, he kept on buying until Berkshire Hathaway (NYSE:BRKa) (NYSE:BRKb) owned 7% of Coca-Cola, or $1.02 billion worth of stock. In three years' time, his stake in the company would be worth more than what Berkshire Hathaway was worth when he began accumulating shares of Coke. Over the years, Buffett's shares have grown more than six times in value, worth some $8.4 billion, or some 200 million shares at a split-adjusted price of just $6.50 a share. He now owns more than 8% of Coke's shares because of the soft drink maker's stock buybacks. Equally important has been the value of the dividends he has received over the years -- worth $1.9 billion all by themselves.

Elected to Coke's board in 1989, he took a passive role, saying that it's been the company's management that has allowed it to succeed. He famously noted: "If you gave me $100 billion and said take away the soft drink leadership of Coca-Cola in the world, I'd give it back to you and say it can't be done."

Yet not everyone will be sad to see Warren go. As big of a force as he's been for improvements in corporate governance, some have said he doesn't always practice what he preaches, criticizing the business some of his other companies do with Coke.

The California Public Employees Retirement System withheld its 12-million vote from Buffett in 2004 because he sat on Coke's audit committee, which allowed the company's auditors to perform non-audit work, which they perceive to be a conflict of interest. Institutional Shareholder Services also urged shareholders to withhold their votes for Buffett because he is an affiliated shareholder on the audit committee, and they prefer having completely independent directors sit on the committee.

Dairy Queen, Moody's (NYSE:MCO), Washington Post (NYSE:WPO), and American Express (NYSE:AXP), among others, are all substantial Berkshire Hathaway holdings that have done significant business with Coke or have received financial remuneration for it. While some transactions might seem like nitpicking -- for example, advertising fees paid to the Post -- others at least lend credence to the appearance of conflicts.

In 2003, Coke provided Berkshire subsidiary McLane with $11 million in commissions related to sales of its products, after paying nearly $104 million for Coke syrup, while Dairy Queen received $688,000 for promotional incentives, paying Coke $2.2 million for its syrup. FlightSafety provided $579,000 worth of services to Coke that year, while Berkshire's XTRA Corp received $129,000 for the lease of trailers used to transport Coke syrup.

Coke's directors stand for election every year, following a change in policy several years ago to improve governance, and some 16% of shareholders withheld their votes from Buffett last year. So the Oracle says he will not seek re-election but instead will concentrate on making new acquisitions.

One can easily imagine that, with or without Buffett on the board, Coca-Cola will continue to dominate brand surveys, commanding the top spot in worldwide brand-name recognition.

Coca-Cola is a selection of Motley Fool Inside Value . Moody's is a selection of Motley Fool Stock Advisor .

Fool contributor Rich Duprey does not own any of the stocks mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.