A potential client e-mailed me some documents related to his project.  I told him that I would not be able to take on his project at this time.

Client: “Then you need to e-mail me back the documents.  They have trade secrets in them.”

Me: “Your privacy is important to me, I’ll make sure to delete them from my hard drive.”

Client: “No. Send them back so that I can make sure that you don’t have them anymore.”

So, I e-mailed them back to him and he was satisfied.