It depends on the jurisdiction (2 party consent vs. 1 party, etc.). It depends if there was an "expectation of privacy." It depends if the image or video is being used for a commercial purpose like advertising. [ADDED: I'm mostly discussing the US here.]
This case is probably questionable but, to your point, if I take a picture of you canoodling in a public park I'm perfectly within my rights to publish that image so long as it's not for marketing or advertising purposes (if people are recognizable).
This case is probably questionable but, to your point, if I take a picture of you canoodling in a public park I'm perfectly within my rights to publish that image so long as it's not for marketing or advertising purposes (if people are recognizable).