well it would appear a little unprofessional even if meant to be light hearted. Would probably result in a "chat" with the safety dept and a reminder of the seriousness of critical stages of flight and FA responsibilities during those periods.
Some airlines do not even allow the use of electronic devices like digital cameras during take off and landing. I guess its nice for the home video or holiday video but the camera man hasnt done the crew member any favours by posting it on the net, even when the FA would just trying to play along and have some fun