Wal-Mart Stores, Inc. (NYSE:WMT) does take some shareholder suggestions to heart, although many of them are quashed by the board. Wal-Mart's board must now be elected by a majority vote instead of a plurality vote, something that has been brought up several times at annual shareholder meetings.

Wal-Mart also said that plurality voting will continue to be used in contested elections when the quantity of director candidates surpasses the number of available positions, which makes sense and is not a change from previous policy at all.

Why make the change to the voting and election procedure now for Wal-Mart? It seems an odd time, but perhaps there is something underway soon with the Wal-Mart board that makes the announcement of a majority-elect board some kind of advantage for the world's largest retailer.

Rob Walton, Wal-Mart's board chairman, said, "We believe that due to recent changes in Delaware law, the majority vote standard is now in the best interests of the company and its shareholders." This is most likely true, although the specific changes to state law where Wal-Mart is officially headquartered would most likely apply to other public companies with registered headquarters located in Delaware.

Bill Ford was booted after five years heading up Ford Motor Corporation (NYSE:F). Bristol Myers Squibb Co. (NYSE:BMY)ousted CEO Peter Dolan only a few days later; his tenure was also five years. Around the same time, it was announced that PepsiCo, Inc. (NYSE:PEP) CEO Steven Reinemund was stepping down to be replaced by up-and-comer Indra Nooyi. His time in the boardroom? Also five years. Jack Stahl was ousted as Revlon, Inc. (NYSE:REV) CEO after ... four-and-a-half years last Monday.

I think I see a pattern. If you're not cutting the cheese (and how) after the end of the fourth annual report under your tutelage, well then, it stands to reason you'll be shown the door. Or, ahem, suddenly find yourself needing to "spend more time with your family."

Michael Dell follows that pattern. Recently, he was faced with criticisms for his successor as CEO of Dell Inc. (NASDAQ:DELL), Kevin Rollins. Rollins' time at the helm? A bit more than two years. It's not enough, Dell said, and affirmed his support for his long-time right-hand man. Dell's troubles, he said, were not yet attributable to him.

Sumner Redstone, though, gave Viacom, Inc. (NYSE:VIA) CEO Tom Freston only eight months. In a move that affirmed Redstone's "eccentricity" (which in this context is a nice way of saying "impetuous" or "hot-tempered"), Mssr. Redstone blamed all his company's troubles on a man who'd only been CEO for less than a year ... hardly enough, you'd think, to evaluate his performance (or for his leadership to have any real impact on the company's stock price).

Is five years enough? Too much? Too little?