One problem related to side/window air bag has been reported for the 2008 Toyota Matrix. The most recently reported issues are listed below.
I was in an accident. My driver's side airbag deployed and then instantly collapsed. It offered no protection whatsoever. I experienced severe pain in my chest and right breast from where the seat belt locked. This pain lasted for 6 weeks. If the airbag had worked properly, it would have cushioned the impact and likely made it possible to lessen the need for the seatbelt to do all of the work. This must be fixed! (my vehicle was in motion on a city street when a person driving the opposite direction made a left turn in front of me and totaled my vehicle. I no longer have the car, but I have a photo of the defective airbag. ).