In a recent usability study, when I asked participants to share some info with their friends, some people clicked the Share button on the page, but some people copied the URL out of the address field in the browser and e-mailed it to their friend. Since this behavior is impossible to capture via analytics, I'm wondering how widespread this behavior might be? Have you observed this (copy URL) behavior in your own usability studies? If so, how often did it happen? I'm wondering if it's a small minority (10%) behavior or a majority (50%+) behavior?