I dont know how correct this is, but...
If you took the picture then you have the rights to it. If it was taken in a public area you have the right to post the picture where ever you like.
If the photo was taken in a closed enviroment, if you want to be able to post the picture anywhere in the public domain then the people in the pictures would need to sign a release form so you can use their picture in public.
That is the way i have come to understand it.
And if someone has taken a photo of you and you want to release the photo in public, then you need to credit the photographer...