formatted data can be recovered, i've had personal experience with this, and some of the tools available are quite good, i was able to recover over 80% of my drive.
There is a better way to 'format' a drive, if you wish to destroy all the data, known as a
Zero Fill. Available in many ways, including the maxblast boot floppy.
There are occassions to format, defrag can definatly put this off for a long time, but eventually it can be a good idea to start fresh.