How much money would you lose if someone typed in yourdomain.net and didn't find your yourdomain.com business? I think Conor presented a valid business strategy for duplicate domains.
Dude, that why I mentioned "gTLDs" (it inccludes .com, .net, .org, .info, .biz, .asia, .eu, etc..), which I think will suffice his wish to be visible. I agree that Conor did bring out a great point. However, I believe that registering the above mentioned extensions will be enough and like conor mentioned, most extensions can be redirected back to 1 popular extension.