What's the downside of an Desmodromic valve system?
I was watching the Ducati motrcycle video, and just thought of this question. What's the downside of an Desmodromic valve system? Why isn't it used on sports cars? For example, if the S2000 used this system it might've been able to reve to 10000rpm or higher. The new M3's engine have a very complicated VANOS valvetrain, but it still uses conventional spings to close the valves. Even the expensive supercars like the Ferrari Enzo and the Porsche Carrera GT doesn't use this system. Why? What's keeping car manufacturers from using it? Is it because of patents? Thanks.