Adding an e-commerce app to your Facebook page can boost sales by 15%.

That’s the key takeout of an analysis of 2000 vendors using the popular e-commerce app Ecwid on Facebook (from free to $17/month), as reported by Vikki Chowney in econsultancy.  The Russian-based developers with US offices received $1.5m of funding in December 2011 and are now rolling out in Europe.

Social commerce needs more ROI stats like this if it is to become – as Zuckerberg has heralded – the Next Big Thing.  Indeed, if a 15% jump in sales could be shown to hold true for large brands and retailers, then f-commerce will have a bright future.  But we’d caution against focusing exclusively on the transactional value of social commerce – we think the true value of social commerce lies in customer acquisition (via fan referrals) and customer retention (via fan loyalty).

And to boost customer acquisition and customer loyalty with social commerce, it’s not what you do  (sell in social media), but how you do it (with fan-first exclusives) that counts.