There's really no law against 1.) taking photos of people at
places where privacy is not to be expected. eg: MRT, shopping mall,
parks, However if the venue is a 'no cameras' or no photography'
zone, or areas where privacy is to be expected eg: toilet, changing
room, hotel rooms, then its a different story. And also, the photo
must not outrage the modesty of the subjects. Other then that, its
the photographer's freedom to take photo of you with or without
your permission.
2.) the owner of a photo is the cameraman, not the subjects. The
owner can post or distribute the photo as and wherever he likes.
However, if subjects in the photo get a court order to stop the
owner if he feels that the owner's action is damaging. And also,
quotes and comments made( by the owner) regarding the photo must
not be damaging. If not, he may be sued.