Tony D - it might appear effective but it isn't foolproof, and you need to be careful that the "format" isn't just wiping the file allocation tables and leaving the data on the disk. Wipedisk type programs do multiple writes of random data to each sector and work better (although the data is still allegedly recoverable even after this). In my previous life at DERA we used Mac the Knife's suggestion, although a hammer was preferred to a rock
Ultimately, it just depends on how sensitive the information is and/or how paranoid you are. The truely paranoid reach for the hammer, but the other options are probably better...
