The site does a poor job of describing how to share your wifi password. After registering and confirming my email address (in most cases, I would have bailed at that point), I'm taken to a page to enter my wifi network(s) name and password. I then set a URL to give to my friends (e.g. http://getwifi.io/wifi-by-ryan).
2 cents: this first time user experience and conversion funnel (likely) would be much improved if they asked me this information up-front before registering and better communicated how it actually works.
Also take a look at Instabridge which shares your wifi network with your Facebook friends.
Believe it or not Windows Phone has a great feature like this that automatically shares access to your networks with your contacts and Facebook friends (if they have a Windows Phone). It even logs into free networks for you without typing, the spam emails as a result are quite annoying though.
Product Hunt
Saasler
Freelance Pro