Only 2 out of every 1000 mobile web users ever tap a custom share button—like even once—according to a Moovweb study. We found similarly tiny numbers during our research designing Philly.com and verticals for About.com. That means people are over 11 times more likely to tap a mobile advertisement than a mobile share button for Facebook, Twitter, Pinterest, etc.
Excellent piece by Josh Clark over at Bigmedium on share buttons on mobile sites. I wrote about my thoughts on share buttons in general a couple of years ago; What’s the cost of sharing? and Increase conversions by removing social media buttons.