I have thought about this a bit, for example, I have lots of Photos of peoples children because babies and kids are cute to photograph. My brothers daughters for example - very expressive and easy to take pictures of but I was hesitant to put them on my flickR... With people I don't know, I pop them online and have never had to take one down yet... Interms of selling an image of a person who is clearly identifiable in your photo, you should get a model release (people have mixed opinions on this) depending upon whom you are selling to... ie: If your image is for a newspaper you may get away with it, but if it's for book / magazine you may need a signature from the photo's subject to clear you... the rights to the image, I think, would be retained by you but they may have some recourse to $$ if you sell the image without them saying it's ok... (I have just worked another 24hr day, so I may be talking rubbish, but I think the above is true and correct, your honour) s.
Just found this little titbit of info:
"The author is the first owner of the rights on his work. Performers are the first owners of the rights on their performances and sound recording producers are the first owners of the rights on their sound recordings.
Photographs are covered by special provisions. The owner of the original photograph, negative or any other original product, at the moment it was made, whether it is an individual or a corporation, is considered to be the author."
Edit... And like Nic, I like the Dan approach, but read the summary - the rest may overwhelm!..
Summary
HERE