Add a link with a similar text to “Tip a friend”, “Send this to a friend”, “Share this with a friend”, that leads to a form to be filled out with the user’s data as well as a private message. The result of the form can possibly be a mail sent out to the user’s friend with a condensed formed version of what the user has found.
This pattern is used when the website owner want to let the users have an easy possibility for the user to spread the word about his site. It can be useful if the information of interest is formatted in a way, that makes it hard to copy-paste into an understandable mail. The website can then help format the mail by setting up the info in a nice and readable format.
The usefulness of this pattern when just letting the user send a blank mail with a link to the content in question, can be debated whether the user in most cases actually want this, or if it is more the website owner thinking the user will use it (or thinking about the impact it will have on his or her site.)
The Tip A Friend page used at Flickr has a pre-filled message box.
When clicking the 'Tip a friend' link at the Danish website woman.dk, the screen is dimmed and the submit form drops down from the top.