After being frustrated about the “Copy Address” function within Mail 4 in Mac OS X 10.6, I have found a solution:
http://macdaddyworld.com/2009/09/14/fixing-copy-address-in-mail-on-10-6
Basically, the trick is to go to Terminal and do the following:
defaults write com.apple.mail AddressesIncludeNameOnPasteboard -bool NO
Hope that helps someone!