The consultancy revealed in a study that the majority of Brazil's population, standing at approximately 195m people, now have access to the internet. In all, 29m Brazilians make online retail purchases.
Such a figure more than doubled that registered in 2008, when 13m shoppers participated in this activity, with the user base growing by around 5m customers per year since then.
In value terms, ecommerce revenues hit R$19bn, or 3.9%, of retail sales, in 2011. These amounts stood at R$11bn and 2.7% respectively in 2009.
"The fact is, despite the gaudy growth numbers, ecommerce in Brazil is nowhere near where it should be," McKinsey said. "Fewer than 40% of Brazilian internet users buy online, compared to 66% in Spain and 81% in the UK."
Looking forward, McKinsey predicted mobile broadband penetration would reach 85% in Brazil by 2015, making this a key channel for marketers seeking to engage consumers.
Regional variations also currently influence the market, with 58% of sales accounted for by the affluent southeast. By contrast, the northeast delivers just 7%.
Many members of the Brazilian web audience are also "socially absorbed", as 87% belong to platforms like Facebook, Orkut and Twitter, bettering the global average of 70%.
"This matters, because in Brazil – maybe more than anywhere else in the world – retailing is increasingly social," McKinsey added. As evidence, some 30% of Brazil's connected community "follow" retailers, while just 12% of British users do the same.
In reflection of this trend, Magazine Luize, one of the country's biggest bricks and mortar and digital players, is already leveraging social commerce.
Pure ecommerce retailers saw revenues rise by 127% in the first quarter of 2012, versus 76% for multi-channel sites. Submarino, selling over 700,000 products in 29 categories, is the leading web-only operator, ahead of Netshoes, which focuses on sportswear, and Dafiti, the footwear specialist.
Among the internet users not buying online across the electronics, apparel or appliances sectors, 23% said they liked to "touch and feel" a product before purchase, and 16% cited disappointing past experiences with online retailers.
Data sourced from McKinsey; additional content by Warc staff