POT...CRACKLE...SNAP!

Advertising campaigns built on the achievements or reputations of celebrities can lose their sparkle (if not their focus) in the blink of an eye.

Michael Phelps' indiscretion with a bong is hardly unique in this context, but it is the latest example of what can go wrong.

Kellogg's did what it thought best to preserve its brand image.

Subway's response appears to be, let's stick with our plan and our man.

Presumably, both companies thought it worth the big bucks they had to shell out to associate their brands with Phelps' achievement, even though the benefit of that association may have a shorter shelf life than they anticipated.

Regardless of which company's action makes more sense to you, the recent phlap reminds us that celebrity campaigns have a vulnerable underbelly.