I really hate writing this, so if this comes off as needlessly harsh I sincerely apologize, but I see a lot wrong with this site.
The first problem is that it's nothing new. I remember sites like this when I was in high school, and I graduated in 2003. Maybe you've built a better mousetrap, and maybe the world is just ready for this sort of thing now, but I'd bet there's a reason there isn't already a dominant site in this area given how long the idea has been around.
I remember from the high school version of this that it was horribly abused. It's a great attack vector for certain types of bullies and misguided prankster friends, and it will be used as such.
I should also point out that people can have multiple email addresses, and not all of your friends and acquaintances will know you by multiple addresses. What if I send the message from the wrong address, and my crush only knows me by something else? If she does like me, she'll have to send her own "first message" to my other address. If I suddenly receive another "someone's crushin' on you" message, wouldn't I first assume that it's someone else, since if it was my crush was mutual, I would have got a confirmation, not a request, right?
So let's assume that the crush is mutual. The only way the crushee to find out who I am is to put herself out there as well. It's sort of a large jump to ask someone, especially a shy someone, to make. Also, what if the crushee knows you by a couple email addresses? Which should she send a request/confirmation to? She could send it to both, but then she's using at least two out of her three freebies. If she likes two people, and knows both of them by two emails, then one of those two people can't receive a confirmation on both accounts unless the crushee decides to shell out two Euros (Around $2.70 in American/Canadian currencies). I sincerely doubt someone would do that.
One major problem is what I'll call "balls." Do women really want a guy who's too fucking timid to just come right out and say they like them? No.
I'll give you an example:
My hotmail address (used for likely-to-spam signups and as an MSN moniker) was created solely to send a "crush" email to a girl I liked in high school. This was back when hotmail had a directory you could use to email people you didn't have a proper address for.
So, I sent her a message saying basically, "hey, we've got a couple classes together and I noticed you, etc. etc." When I got a response back, is was just "You've piqued my interest. Spill, who are you?" with instructions to just man up and approach her in class. Women tend to like confident men, and men who hide behind internet filters tend not to be the confident type.
Finally, I just want to note that there's also a question of legality here. I can't cite a source off the top of my head, but I know there is legislation in Canada and possibly in the States that classifies "Tell-a-Friend" type email functionality as spam. These emails are therefore subject to fines. I don't know if they enforce it for things like this, but it's definitely something to consider.