While it is true that some people may be motivated by taunting and good-natured teasing, step counts with cheers do not take into account that there may be some people we would wish to engage in this sort of teasing, but others we would wish to leave out. One of my FB friends is someone who formerly logged a half-million or more steps per week, far more than myself. Following injury, she isn't yet making 10K a day. I do not send her cheers now, because it looks like "Haha - who's having trouble keeping up with whom NOW!" In fact, unbeknownst to me, I most likely had been sending that message when you made the change without informing users.
Some people have hailed the change to limiting the bullying to only those within 10,000 steps as movement in the right direction. This is "a step in the right direction" only in the same manner as the bully who decides that he is only going to steal lunch money from the kids in his own grade level instead of also stealing from those who are younger.
I implore Fitbit to revisit their "solution," as it is actually not a solution at all.