Discontinue E-Mails

No

e-mail marketers must include a visible and operable unsubscribe mechanism in all emails.

Clicking unsubscribe tells the sender that you have a functional email address. That makes your address all the more marketable.

Just put it into your spam folder and move on.

^Seconded.

If you don't recognize the email source just send it to your spam box. If you do recognize the sender and remember that at one time you were involved in some kind of legitimate transaction (buying something online, subscribing to a newsletter, etc...) and now don't want any further email from that source? By all means, click the unsubscribe button.