paper by Peter Gutman discussing drive technology and data recovery,Some may find it interesting. Basically He says its impossible to completely remove all traces of data (hard drive and even RAM)with modern recovery equipment, best you can do is to make it more difficult and expensive: taser1 http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html
Seems to me all the wiping procedures are trying to get the signal level below the imposed noise. Instead of using random or arbitrary wipes how about overwriting with similar signals? The best way to hide a printed message isn't to scribble random lines over it; instead you print repeated messages in the same font over it until you can't distinguish the original words. If I wanted to overwrite an encryption key I'd generate multiple keys of the same length and use those for overwriting. Multiple variations of the same kind of data on the same place on the media should make it impossible to know which is the original.
Ive found that one of the best methods I have ever seen was afforded to me by a neighbor..... The BBQ! Seems to be quite efficient at erasing all traces of any information inside one's hard drive! Bill