The chief of advertising at global retailer Wal-Mart Stores, Inc. (NYSE:WMT) has left the company. Julie Roehm, the head of advertising who led the selection of Chicago-based DraftFCB as the retailer's new ad agency, will be leaving Wal-Mart after less than a year on the job. Now that was a short tenure.

It is unclear whether Wal-Mart will reconsider the hiring of DraftFCB or alter its marketing strategy, but given the timing it is likely that Roehm's departure is tied to her decision to hire DraftFCB as Wal-Mart's ad agency. Apparently, the ad agency has has had little success preventing Wal-Mart customers from defecting to other stores like Target Corporation (NYSE:TGT).

In addition to Roehm, Sean Womack -- vice president of marketing -- has also left the company. Hmm -- two marketing execs leaving at the same time? Suspicious. I think Wal-Mart's image as a dirt-cheap retailer is still intact, regardless of its efforts to move into higher-margin goods and even offer organic food and produce to its customers. Can Wal-Mart ever change its focus and image from a retailer of all-things-Chinese-made to higher-margin-retailer-with-appropriate-marketing? That will be like turning the Titanic before it sinks.

Proof is in the pudding, as sales at the retailer have been sluggish. When Roehm was hired and then herself hired DraftFCB, the moves seemed to signal a change in marketing focus to highlight different goods and rely on a more highly targeted approach to reaching consumers. It didn't happen, as Wal-Mart's holiday season advertising message has reverted to being all about low prices. And that may be all it's ever known for.