That depends on the drive, but generally it's not a good idea to shock it ^_^. Some models are marketed solely on their resiliency. You should check out the wikipedia entry to get a general idea of the parts insidehttp://en.wikipedia.org/wiki/USB_flash_drive
Generally, the smaller a process used to make the components the more sensitive they are. If anything I'd say you're likely to break the controller in which case it may still be possible to access the data on the flash chips providing you are skilled and patient enough.