Canon's new Rebel T4i (a.k.a. EOS 650D) has a new "hybrid AF" mode, which allows continuous AF during video, but only when used with one of the new [STM lenses][1].

I've seen chatter on the web forums where it's suggested that this is a greedy move from Canon in order to force people into buying new lenses. I understand that STM allows a better AF experience during video, but is there a technical reason an STM motor is a _hard prerequisite_?


  [1]: http://photo.stackexchange.com/questions/24109/what-does-stm-mean-on-a-canon-lens