UPDATE: Read InnoCentive's response at the bottom of this post.
Why on Earth would someone make it harder than necessary for visitors to tell their friends about a web page?
But this is exactly what many websites do.
See for example InnoCentive, which connects organizations hungry for breakthrough innovation with a global network of creative thinkers. While visiting their site another day, I spotted a challenge that I thought might interest a friend, and clicked on their "Refer-A-Friend" link, only to be brought to this page:

Is it really necessary to make a person register to simply send a URL to a friend? And, after you register, you have to wait for the confirmation email so you can click on a link to activate your account. I went through the entire process (just to be able to talk about it here) learning that in reality it is meant for people interested in earning money for referring a challenge winner. I couldn't find the option to send a link to a specific challenge: people who simply want to spread the word, and aren't interested in the financial aspect, have to go to the trouble of copying the URL from the browser and opening an email application to send it to a friend.
Now contrast their approach with that of yappr.com:

Yappr is a community for English learners. As a guest visitor, you can watch videos and quickly send a link of a video you liked to friends using the "Share it" option. (A clearer indication that "Message" is the only optional field would be nice, but sharing is still a pleasant experience, particularly when your friends have a memorable email address.)
InnoCentive's bad user experience, on the other hand, doesn't end with the Refer-a-Friend feature. If, during the registration process, you submit the form before all required data is input, you will be punished with a request to reenter the security code, even if it was correctly entered the first time (and if someone tries to tell you that there must be some good reason for this inconvenience, take a look at the previous post about Twitter).
It's already difficult to get people to actually want to tell other people about you as it is. Why not give users instant gratification, letting them quickly fill out a form with the minimum information necessary to help spread the word?
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UPDATE: We are happy to report that InnoCentive is working on improving its UI mechanics to allow non-registered visitors to refer a challenge to others (hopefully they will also make their registration form more user-friendly in the process):
Dear 2wtx,
There is method behind the Refer-A-Friend madness on innocentive.com! The rationale is that Refer-A-Friend allows someone who has registered to be an InnoCentive Solver to refer their friends to become Solvers as well, potentially earning money if these new Solvers solve Challenges and win awards. Only registered Solvers can refer their friends, so you need to register before doing a referral.
But the real problem here, as you pointed out, is that we don’t have a clear, simple way for people to refer Challenges to their friends, which is what you were looking for. (That’s not what Refer-A-Friend is for.) There is an “Email this Challenge to a friend” link, but to get to it, you need to click through a “Read More” link that currently requires login. The good news is that we are working on much better share-this-Challenge capabilities – stay tuned!
Regards,
Walter Gillett
Director of Research and Development
www.innocentive.com
