I cannot see one good reason for this feature, which incidentally is enabled by default. Would it be better to disable it by default and right mouse click to launch?
Let's hope Windows 7 has this Trojan assistance taken out.
This is a very good in-depth article on this kind of attack using autorun/autoplay.
The concluding remarks from this article is worth quoting here:
Ignoring the DMA scenario for a moment, the success of the attacks I have discussed, as well as the success of the countermeasures, will depend on the privileges of the user using the computer. If the user is a standard user, the amount of damage the exploit can do is limited. It can still steal that user's data and anything that user has access to. However, the attack will likely not impact the network at large.However, if the user being exploited is an administrator, the consequences can be a whole lot worse.