Facebook commerce provider Ecwid reported that its customers with stores on both Facebook and external websites credited the social network with 22.1 percent of their total revenue in the second quarter, up from 17.7 percent in the first quarter and 15 percent for the full year of 2011.

Ecwid added that average second-quarter revenue for its Facebook stores was up 38 percent compared with the previous quarter, and its total Facebook stores grew 26 percent during the same time period.

The company powers some 180,000 Web storefronts in 174 countries, and around 40,000 of its clients — mostly small and midsized businesses — also have Facebook stores. Founder and CEO Ruslan Fazlyev added:

Despite highly publicized big-brand Facebook store withdrawals, our data show that F-commerce is growing for small and midsized businesses. We’re still in the early days of social commerce and, since the rules of this game are still being written, it’s important to pay attention to who’s figuring it out first. Right now, that’s the SMBs.