Is it safe to have your camcorder placed outside of your vehicle and record while driving in the highway?

I'm concerned about how the rushing wind will affect the audio component of the camcorder.

Thanks for your time.

If you've got a mount for it, and a safety cable, then there is no problem with normal driving speeds on a road. Filmmakers do this all the time.
You might want to check out this book from Dan Selakovich. He shows how to build a very safe mount for next to no cost whatsoever.
http://www.nabstore.com/template.cfm?Template=/Ecommerce/ProductDisplay.cfm&ProductID=1873
As far as the audio, of course it would be affected by wind, that's why you'd either
a: use a wireless or wired mike to feed camera
b: use a second recording system to capture audio and then sync in post.

The other concern would be damage to the camera from little pieces of "stuff" hitting it, especially at highway speeds. I tried this several years ago with my VX-2000 using the Sony wide angle lens and ended up with a chip in the middle. I guess a little piece of gravel hit the lens. You should use a UV filter to protect the lens. Unfortunately, that wasn't an option for me because the Sony WA doesn't have filter threads. Anyway, it was an expensive lesson to learn...

Make a plexi glass box to put around your camcorder.

Make a plexi glass box to put around your camcorder.

Yeah that works good. We put our video camera in a plexi-glass box and put it inside a car we were blowing up and got some amazing footage.

The people on The Amazing Race do it all the time! And they use DigiBeta!!! They always get a shot from the side of the front doors of their car! (low speeds only).