• by Robert Passikoff , Op-Ed Contributor, October 14, 2010

L'Oreal has announced a new addition to its roster of celebrity spokespeople, signing actress Julianna Margulies as a new ambassador and celebrity face for the brand. Margulies currently stars in the critically acclaimed TV series "The Good Wife," for which she won a Golden Globe and SAG award for her portrayal of the loyal yet betrayed wife of a politician.

Were you surprised that L'Oreal (and most other beauty brands (both luxury and mass merchandiser) went the expected route and found a high-profile beauty to front for their brand? We weren't. But just because it's predictable doesn't mean it isn't practicable, and there are two basic ways a celebrity can positively affect a brand.

The first is by creating what might be called "borrowed equity," when the celebrity brings more attention to the brand than otherwise might be the case, an approach usually used when a brand is seeking high levels of awareness.

The second is when the spokesperson association actually increases the brand's equity -- that is, when the values inherent in the spokesperson significantly reinforce brand values. If successful, the brand is then seen to better meet, and can even exceed, expectations that consumers dream about for the ideal in the category.

That measure -- the brand versus the real, unconstrained-by-the- marketplace Ideal -- is the very best measure of brand engagement and loyalty because it takes into account real emotional values, something that imagery and good-looking celebrities can't bring about on their own.

Margulies won't appear in advertising for L'Oreal Paris until 2011, but until then, we turned to the Brand Keys' 2010 Loyalty Leaders List to see which brands were currently engaging loyal customers.

Here's the top 10:

1. Mary Kay
2. Maybelline
3. Estee Lauder
4. Clinique
5. Avon
6. Lancome
7. L'Oreal
8. Cosmetics
9. Chanel
10. Max Factor

Coco Chanel is said to have offered this bon mot: "Women have two weapons -- cosmetics and tears." Happily, these days beauty brands can arm themselves with something more than outdated clichés: the loyalty driven by real emotional connection.