I never put "copyright (c)" and date and name on my work, but what I do do, is make sure I have my name and a contact number on every page of the document (usually as a very small header, about six point, so it can be read if it has to be, but isn't "in yer face"). This means that if my manuscript gets seperated from my original letter, and someone finds and likes the work, they can always contact me.
What the hell do you do if you find a good piece of work at the bottom of a slush-pile, with no contact information, but just happens to ring all the right bells. It must be tempting.
I used to be an artist in the computer games industry and have had experience of portfolios being photographed and CDs being copied while the interviewee is taken on a tour of the building.
Just thought I'd throw that little anecdote in to fire the paranoia.
Colin M.