Noone here is saying that they don't have a big influence, but I believe that a normal, well raised, intelligent human being can not fall for that one.
Besides, I don't think that it really is that way in the entire entertainment industry, cause there are a lot of actresses and others for example that are not only skin&bones, and are still found beautiful - starting from Scarlett Johanssen to Jennifer Lopez, Eva Mendes, Beyonce..and other actresses like Penelope Cruz, Halle Berry, Uma Thurman and Sharon Stone, aren't that "round" like these above, but definetely can not be considered as those without feminine curves.
Only models are those that are that skinny. I don't know who started that trend, cause when I was a child, a teen, they weren't that way - Claudia Schiffer, Linda Evangelista, Cindy Crawford..they never looked like skeletons...and I really don't know anyone who finds that beautiful, that's why I do believe it's a psychological illness of some kind, or even it's consequence, and that really needs treatment.