I just looked at a profile photo taken with a cell phone. It wasn't nearly as flattering as the person taking the picture hoped it would be. Her face was distorted, due to lens length and distance from the subject. In theory, a lens' length is measured as the distance from the first piece of glass in the lens, all the way through to the piece of glass at the back of the lens. A 50mm lens is about 2" from front to back, not including all the mounting hardware. All cell phones have very short lenses. They don't have the room for anything else.
This illustration is from Ed Buziak's Photos + Artwork Blog, and you can view the original at http://blogs.salon.com/0004217/2005/07/18.html
Left image taken with a 20mm lens (super short!) at less than 12" from the subject. Center image taken with a 50mm lens (medium to short) and he didn't mention the distance from the subject. Right image taken with an 85mm (medium length) lens at about 4 feet away from the subject. I think of any lens that is 100mm or more to be long, but that's just me.
These demo photos have been shot with the camera 'nose to nose' with the subject. When shooting with short lenses, whatever is closest to the lens will appear much larger than something even 1/2" farther away. If the camera is above the subject's face, the forehead will look larger. If the camera is below, the chin will seem larger. But the feature you notice most is usually the nose. It's always bigger than it should be and that is rarely flattering.
It looks like the subject's posture has changed as well. In the left image, it looks like he is sticking his head out towards the camera. In the middle image, he looks like he is leaning forward. He isn't. That's just more of the distortion at work.
If you can, imagine what you would get if you were to use a short lens to photograph a person with poor posture, who sticks their head forward as they slouch. Then, have the camera above them and use the on-camera flash that flattens things out still more. Their oval face will become a triangle, their nose will look like it's broken and swollen and there will be almost no space between their very big nose and their small mouth. If part of their body is visible, it will look too small to support that head.