"..so do not panic when you see a soda can.." Ding, Ding - We have a winner. I'm just astounded by the reactions on a supposedly 'conservative' site. Your comment hits the paranoia nail on the head, but you are surely going to get flamed. We gotta watch out for the children, don'tcha know.
http://www.devilducky.com/media/56891/
Here is a great car bomb vid- you can see the air shock moving away.
If you freeze the vid at the beginning, you can see that there is nothing to give the nature of the thing away.