Invite / tell a friend

I would like to hear what people here say about the invite/tell a friend site promotion technique.

Does it really helps a site?

Can this considered as spam?

Have you ever used it? What was the results?

Thanks :)

I have used this option to a site, with no luck at all.

But I know that many sites get many visitors from this technique.

As for the spam, I don't think you'll have any problem, at least I haven't

PS: Welcome to our small community :)

You may also find this thread usefull :

http://www.webdigity.com/index.php/topic,126.0.A+simple+mail+to+friend+script.html