yeah but you really need to kick it in order to get it off.If the force is big enough to yank off a magsafe cable, it should be good enough to yank off a USB plug. The question is do you just want your data to die, or you want your USB port to go with it?
using magsafe for a few years now, never really had it accidentally disconnect.
Also the magsafe/Light Peak cable you see will probably be used for connecting between machines (macbook) and monitor (Cinema display/iMac).
Just like when apple made USB standard on all macs. There were no accessories, everybody was either using ps/2 or adb. Everybody (apple haters) claim that it's apples plot to get all the stupid Mac users to buy their overpriced USB keyboards.