Tip A Friend
Problem summary
The user wants to share something of interest with a peer.
Example
Usage
- Use when the user might want to spread the word about something on your site, but find it difficult to shorten
- Use when the user might think something on your site is interesting for other people than himself.
- Use when you want to let the user have the ability of easily spreading the word about content on your website.
Solution
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.
Rationale
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.)
More examples images of the Tip A Friend pattern
| From movies.yahoo.com | 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. |

I never use these because of the risk of the website harvesting my friends’ email addresses. It is therefore a broken pattern.
Not only that, I don’t know anyone who will thank me for delivering him some extra spam. If I dó find something thats só intresting I want to inform someone, I’ll just send a mail with the url, I never use a “send a friend” link.
As a website owner, keep in mind that this function could be misused by bots to automatically send spam to any e-mail address in the world right from your server.
Discourage spammers by omitting the “optional message” field.
I think, we can gladly abandon the “e-mail-this” approach for most applications, because of the spam problems and the ¿fact? that nearly nobody ever uses it. The IM/social network this option should stay and be developed, though. Consider that the Digg this button is just the e-mail this button evolved.