Our website has several areas with “invite a friend” type links, and for the most part they just pop up a modal asking for your name, email address, friend’s email address, friend’s name, and the ability to modify the message of the body.
The huge upside to this is that anyone can easily send a message to their friends without having to worry about their computer handling mailto: links the way they want them to.
The huge downside to this is the level of spam we get.
Typically if the same IP tries sending email out on our system more than once in a short period of time it will enforce a capcha, but a few clever bots have gotten around this recently.
What do you use for the public to share via email?