Such a feature is worth having considering the "mouth-to-mouth" online marketing technique recommendation/new visitors conversation ratio.
Your visitors may wish to refer some of your Web site pages or articles to their friends.
This is where you need the "Recommend to a Friend" feature which will allow your visitors to refer your pages. It also allows you to fully customize the recommendation message.
* click on the image to enlarge
This is an "Email to a friend" implementation sample from Bioteams.com
In order to be able to send the page to a friend, the visitor should click on "Email to a friend" and a form field will show up.
* click on the image to enlarge
This is the "Email to a friend" form fields sample from Bioteams.com
This shows up only after the visitor clicks on "Email to a friend".
Your benefit here is that you could get more targeted visitors and so make your Web site more popular.