I take thousands of photos a week. For each job, I'll try to get a large number of different angles and set ups so that my client has as much choice as possible. Clearly, there will some that are better than others. There are also many images which are simply unusable because people have their eyes shut or are pulling silly faces simply in the normal course of holding a conversation. To my mind it is unfair to publish these images because the person is not deliberately pulling a silly face. If they are doing so deliberately then they are fair game.
But if a picture is amusing because of the way a person is holding their body then I think that is fair game.
I didn't take this image and cannot immediately source who did as it was posted to a Facebook Group - I'll happily credit the snapper as soon as I know and am only posting it here to critique as part of the wider discussion.
UPDATE - the picture came from a Times WBLG caption competition but it was uncredited there so could have been a Times snapper or an agency.. Will keep on digging