I find it interesting that this subject has come up a few times, including a problem that I have run into recently along the same lines. I have discovered many a time when I have done a job for somone, that they automatically assume that the photos I take for them, belong to them outright. Meaning that they own them and expect that you won't use them for anything else, whether it's for commercial gain or just for your own portfolio. I don't know why it is but here in Singapore it seems to be so. Anytime a photographer picks up his/her camera and snaps a picture of someone or something, he/she automatically owns the copyright to the photo, regardless of any agreement that is produced. It should be standard industry practice that this is the case but sadly it isn't practiced, or even made known that the copyright belongs to the photographer. Sure the photographer can give all rights to the client but certainly a substantialy higher fee should be negotiated. Think about this for a minute. You snap a photo of someone and you freely give up your copyright to that person. They could easily take that photo and sell it for commercial gain and earn an untold amount whereas you are the one losing out. I believe though that in order to be crystal clear with everyone, that an agreement should be produced upfront and agreed upon even before a picture is taken. That way you can then decide whether you want to take or not. If you easily give up your copyrights to the person without agreeing upon a higher fee, then you will set the stage for it happening over and over again and you will expect that this is common...which in fact it should not be at all.
I recently had this issue with a magazine that hired me for a shoot. I took the pictures, handed over the images on a disk and then put up some select images on my portfolio. The magazine came back and said I wasn't allowed stating they owned the copyright. I laughed at them and said no you don't. I then received a contract after the shoot was over and done stating the same thing. That any images I take belong outright to them and can be used for worldwide coverage. I told them that I'm not signing the agreement, nor will they own the copyright to my work unless they pay me more. In the end, I won. I can use my work for my portfolio but it also means that they probably won't be using my services again. It's all about standing up for your rights and sticking to them. Don't let others walk over you and demand that they own the rights to your hard effort and work. Good luck...