Ram USB storage device
RAM chips have a limit to the number of successful writes and reads. They are just higher than Flash chips. And ram is just as likely as flash to die. And RAM does not have the storage capacity of flash.

Given that, and you knowing that it will be volatile, there is no reason you can't use RAM as a flash drive. You would need a custom controller that handles the USB to storage interface. Though I suspect it wouldn't be much different than a standard usb to flash controller, the concepts are the same. You'd be creating this from scratch though. 

Keep in mind that the main benefit if RAM chips is speed, which you will not benefit from as usb and overhead will be your bottleneck.