For clarifying this.... Flash drives has nothing to do with the way HD drives work. While fragmentation is bad on HD drives because of the way they access the data (if the data is written secuencialy the read of all of it is done without moving the magnetic heads, while if fragmented much time is wasted in repositioning the magnetic heads) on flash drives the data is accesed without any mechanical parts having to move so the access is constant for all the memory cells wherever they are. So defragmenting flash drives isn't so good idea...