I think Adele is very pretty and has a great voice, but she's hardly Sinead O'Connor. Patti Smith, or Maya of M.I.A. who were/ are all controversial despite their popularity, as well as having garnered an alternative cache. Adele sings about heartaches and relationships and the majority of her fans wouldn't bat a lash had she agreed to the L'Oreal deal-- I'm sure they would identify with her more had she been the new face of the brand, actually.
I mean, good for her for not wanting to be a corporate face, but her music and image is pretty generic so I don't see how it would harm her artistically. With that kind of money, she could contribute so much to any social or political organizations if she doesn't want to keep the money for herself. Money isn't everything-- but try to do something, anything without it and you'll quickly realize how much of an importance it really is. I find it more selfish when stars turn down such deals for their artistic integrity.