Yes, you can use a web cam to produce a choppy online video with horrible sound, but you're likely to lose credibility in the first few seconds. You can get a big edge over the average video blogger by choosing a good tripod, microphone and camera for the web.
This shows 2 methods for faking a person being hit by a car. One uses Adobe Photoshop and editing software, requiring time & effort to add realistic detail. The other method uses camera angles to imply the collision.