In many e-commerce systems, there is a feature "to tell a friend", you could email the product information to a friend through an online form.
Of course, this email script should check all the validation to avoid email header injection attacks etc.
My question is that there are so many spams today, will "to tell a friend" feature do your site good or bad now? As a user, will you open an email like this if a friend of you asking a site to send "to tell a friend" email to you?
Thanks!