Ya, I've thought of that before too, or read it somewhere. It would be interesting if some one created a way to make it so that you could move the camera along the track in more precise increments(I don't know if they're really needed or not).
Time to go see how much train tracks are fetching for nowadays on ebay.
Okay...
I went and looked on ebay. The prices still seem kinda expensive, around 10 bucks and up with shipping. It would probably be better to get something of the sort at a garage sale for a few bucks (makes me wish I kept the train set I had a long time ago. It was cheap, and a perfect size). The trick is to also find something that is big enough to support a camera, a car for the camera to sit on, and a track that is cheap(no need for electric stuff on it).
http://cgi.ebay.com/LARGE-TRAIN-and-three-cars-and-some-track-Display_W0QQitemZ290231167598 QQihZ019QQcategoryZ130QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
That was one I found, it was similar to the one I used to own.
If anybody else finds more interesting info, post it here.