Data detectors watch for addresses, dates, and times in e-mail messages, and when found, highlight those regions of text, they display a button to show a contextual menu. If you activate the contextual menu, you can create new iCal events or Address Book contacts based on the highlighted information.
Some people like these features and some don't. I find it annoying, sometimes when you just want to copy the email address from an email and when you paste into something else like Bento you get the name and email address like below.
Craig Richards <email@example.com>
There is a simple way you can disable these. Open a terminal window and type in
defaults write com.apple.mail Disabledatadetectors yes
This way you will only get the address
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