I haven't researched it myself, but according to the first link I provided as a consulted source, the blogger felt that wiping with zeroes was secure enough for most users. I agreed with what he said. My really personal stuff was under a TrueCrypt partition, so even if someone is able to undo the writing of zeroes over the whole drive, they then need to know that the TrueCrypt partition existed and the correct passphrase to open it.