I didn't read all the responses, but to the OP, I'm glad you didn't get injured.
As far as the jack goes. The OP should have EVERY expectation that the jack should be able to hold the car up, and that it is ridiculous if it failed and stripped, etc. I would be fuming!
All that said. You should NEVER put any part of your body under ANY jack, PERIOD! Always support a car when working under it.
Also it should ONLY be used on flat and level ground with the wheels chocked, otherwise it can, and probably will collapse, however, this is very different from it failing when used properly, like I understand that the OP attempted to use it. Also as others had stated, don't use it to support the weight of the car if you are working on it, because the rocking motion may also collapse it. Jack stands MUST be used.
It is an emergency jack as others have stated, use it only in roadside emergencies VERY CAREFULLY. There is no reason that an owner shouldn't be able to use the jack more than once either. They should be able to use it 1000x if it was engineered properly.
All that said, I would definitely let VW know that it stripped / failed, I feel very strongly that it should have never happened, and that it should have a safety margin on the weight that it is capable of.