Exactly, I was going to point out the same thing. The flash cells might be charged or discharged of electrons, but the whole flash drive can't have a net charge

Exactly, I was going to point out the same thing. The flash cells might be charged or discharged of electrons, but the whole flash drive can't have a net charge or else you will certainly feel it. And because no solid/liquid/gaseous matter is exchanged between the computer and flash drive, there are no positive particles (nuclei/protons) moving either. This is similar to what it means to "charge" a capacitor. It doesn't mean injecting or removing electrons from it, because that would cause a net charge. It actually means shifting electrons from one electrode to the other, separated by an insulated gap. http://amasci.com/emotor/cap1.html http://amasci.com/emotor/cap1.html