Wow, this is a long thread. I am a professional published photographer. Here's my "opinion"
1. Whoever takes a photo owns the copyright. If you ask your friend to take a photo of you using your own phone, your friend owns the copyright to that photo. On the other side, the model owns the "likeness".
2. The copyright holder has control to what happens to the photo. However, there are limitations. For example, an ad company wants to use the photo. This would be a money making venture, the copyright does not extend. The copyright holder needs to get permission from the model to use the "likeness". . Same thing if that photo is to be published in a magazine.
3. "Model Release (contract)" - This is probably the most misunderstood document in modeling/photography industry. When a model signs a model release, the model is "releasing" rights to the likeness to the photographer. Most of the time, all rights are being released or given to the photographer. The photographer/copyright holder can now do anything with the photo. This includes anything for profit.
4. How would models protect themselves? First, do not sign a release, this is especially if you are paying for the session. If you are paying for photographer's services, ask the photographers to relinquish copyright to you. Now, the model has control. If the photographer, for some reason, wants to use your photo, that photographer will need a "license" to use your likeness.
5. "License to use likeness" - This is where the big bucks come in for the models. You can give full license, restricted license, license with limited time or expirations date ...etc. The models in the campaign ads in magazines are paid the big bucks not because they showed for a shoot but for the use of their likeness.
6. Summary, a photog can do whatever he wants with a photo as long as he is not making off them. He can put his watermark, post the photos on FB or forums, even use for educational purposes. Models has to give a license to use the likeness if the photo is to be used for anything for profit.
So... wants to shoot with me? haha