If you’re implementing the web share API on your site BEWARE. The API takes three arguments, Name, Text, URL, but when sharing on iOS it will only pass two arguments and omit the third one, the URL (go figure, the most vital piece).
Jeremy has a modified script that he uses to only pass across the title and URL and has also logged a bug with Safari/Webkit (thanks Jeremy).
Some additional resources
An excerpt from The Web Share API in Safari on iOS