sorry for resurrecting such an old thread, but it came up on a search i did for complete phone wiping methods.
the method described is like wanting to completely format your PC, but actually deleting the cookies in your browser.
factory reset wipes personal data (about 50% of it). it does not, in any way, count as a hard reset or wipe.
that being said, i was hoping someone would actually know a method to wipe the internal memory completely, shred the resulting free space with a (minimum) 7 pass random rewrite and install a fresh ROM.