[Ultima]

To add to what others have said flash drives actually have special programming to balance out the read/write usage of the drive among its different sectors. The result is that the data on the drive is spread throughout making it look like a normal harddrive that needs to be fragmented. Of course as has been said flash memory doesnt have mechanical seek latencies so there is no performance penalty.

Summed up: DO NOT DEFRAG FLASH DRIVES! SD or USB it does harm with no good.