I like the Chanel ad, but it screams 'va va voom!' which I don't associate with Chanel, in any of its incarnations, at all. Whoever posted upthread that she's more an A&F or Versace girl were right. Blake may be feminine and modern, but her style is more Marilyn Monroe rather than Jackie Kennedy.
I don't know if anybody here reads InStyle, but the US March 2011 issue, has another endorsement for her from Lanvin who says "Women are powerful; their strength is internal. They need a wardrobe that lets them be themselves instead of what some designer thinks they should be. That's why there is a return to practical clothes, and when I say that, I don't mean boring. Just look at Blake Lively, who likes gowns she can strut in. That is pragmatism at work." (197) (The article includes a picture of Blake awkwardly holding a gown with a split up the center.)
If that wasn't enough, last month, in the Feb 2011 of the US InStyle, there was a interview with Michael Kors who was asked about his favorite fashion icons and he named Blake as one of them, with these words: "Dressing a quintessially California girl can be difficult. But Blake gets it; she always chooses audacious yet keeps it simple." (100) (The picture accompanying is better: Blake is in a strapless orange cocktail dress with nude pumps.)
I think Kors nails Blake's style but I think he overcredits her. Lanvin seemed to be just namedropping. I like Blake's California girl style, but she hasn't put her own unique stamp on it. It's all over the place. Also, even though it's been said before, it always bears saying again: she never seems to be properly fitted in her gowns.