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.
what if its taken in a lift?