Actually, it really depends on the vehicle. Some vehicles need just a small sharp thud on the front to deploy the airbags, like a swift kick or... as in another (true to life) video... a lady's handbag across the front bumper. Others aren't this sensitive, but any airbag-equipped car will deploy an airbag if you drive head-on (straight, no angle at ALL) into a wall at 20 km/h.

And, from the other thread, the situations depicted in the first post are exactlythe same situations cited by other manufacturers as cases in which airbags will and will not go off.