My best guess is that Ember is marketed as "omg look awesome!" and Angular is marketed as "hey, this is useful", and this causes the user community compositions

My best guess is that Ember is marketed as "omg look awesome!" and Angular is marketed as "hey, this is useful", and this causes the user community compositions to differ just enough for this to be the case (though there are still crazed fanboys on both sides, hence the Ember<->Angular comment thread wars).