This brings up a question I have often wondered. Isn't coasting long distances down hill the same thing? In other words, if I was at the top of a hill, and put the bike to in neutral and coasted down, same thing right?
Coasting is free wheeling..not in gear, clutch disengaged. Towing the bile that way is the same as free wheeling. The only thing the wheel is turning is the clutch and trans input shaft.
As mentioned concern of it popping into gear on tow it would be a idea to tie the clutch lever in but that may also increase the chance of it slipping into gear as the trans input would not be turning, but with the lever tied back it wouldn't mater if it did as the clutch is not engaged.
You can get tow buy the front wheel units.
http://www.motorcycle-rack.com/MFWT.html