Take a look at this HDD destruction service offering:
Essentially, you pay them $20 and send your old disks, and they send you back a 'certificate of destruction' that promises they turned the thing into dust and recyclable shreds.
I understand that data destruction is important in many cases, but what do you think of building a mail-order service around the mechanical obliteration of disks?
Is such a service worth spending $20 on?