Duolingo is open to the public now, are invites still necessary?

Now that Duolingo is public and anyone can join, I've found a good way to "invite" people is to send them your Duolingo URL. I've added mine to my e-mail signature. For example mine is:
http://duolingo.com/#/garyweir

Since they are not logged into Duolingo, they will see something similar to this screen capture:
http://garyweir.org/duolingo-garyweir.jpg

Thanks, I had a sense it had opened up.