Sorry, someone else asked if they could put Wonderboard on their house today, too.
Melamine is a finish typically placed on particle board. This product DOES NOT like to get WET. It will swell, mildew, and disintigrate. ICK!
Melamine typically comes in 1/2" or thicker panels (VERY HEAVY), but not usually in a 4x8 sheet, so it would be tough to actually SIDE a house with it. I can't imagine having to predrill all of your holes to countersink your screws without destroying the finish of the melamine, having to make sure you hit the stud EVERY TIME, or else leaving extra screw heads in the finish. How would you flash between panels to prevent moisture penetration?
How would you repaint the house someday? Melamine does not like paint.
How would you explain the melamine to a potential buyer? This is not a proven construction material for this purpose.
If you are really looking for an unusual but very cool siding, check out Hardiplank siding, manufactured by the James Hardi Corporation http://www.jameshardi.com.
No, I do not get a "kickback" for promoting the product, I just like it.