They have created (also re-modeled) brand identity for may companies including GE, Unilever , Sony Ericsson, Mercedes-Benz ,Tata DoCoMo ,Hero MotoCorp. I was wondering why I didn't know of this company before.

What interested me are two things. If you look for their logo on their website, you'll never find one. Wolff Olins never created a 'logo' for themselves other than a yellow patch that they generally associate with. All I could see is a peculiar way of writing their company name. And that too is used in different styles at different places (a la Google drool way ). That brings the point - having no identity is also an identity! Obviously they asked the few critical questions that needs to be asked in any identity creation process : Do we need an identity? Yes. Do we need a logo ? Nope!

Of course they have the identity, but they have not gone for a logo as a means to communicate that identity.

I was watching their director Charles Wright on TV. He said something interesting when asked about setting up shop in India.This is the second interesting point that I mentioned. The corporate houses in India are willing to pay a premium - or even to business with them - because it is an international consultancy( "you know our logo is done by a New York based firm!" ). So Wolff Olins didn't want to dilute their brand equity. They know how to manage their brand well. Geography does matter in perception.