Boston based BzzAgent has been acquired by UK based dunnhumby, Ltd., a data-centric leader in building brand loyalty for consumer packaged goods and retail companies. dunnhumby is a wholly owned subsidiary of $140B retail giant Tesco, the third largest retailer in the world based on revenues after Wal-Mart and Carrefour (second largest after Wal-Mart if you go by profits).

Sources close to the deal tell BostInno the financial terms dictate that BzzAgent will be acquired for $60 million, which will formally take place after BzzAgent meets a set of milestones in the upcoming months. BzzAgent will become a subsidiary of dunnhumby and continue to operate as a stand-alone business.

dunnhumby, with the tagline “essential customer genius,” uses loyalty card data to help manufacturers and retailers understand in-store habits and ultimately market their products better. Its client roster includes well-known companies and brands like CocaCola, Heinz, Nestle, T-Mobile, Vodafone, Unilever and P&G. dunnhumby was interested in complementing its 200 million loyalty cardholders’ data with BzzAgent’s analytics-centric social marketing expertise.

BzzAgent’s founder and CEO Dave Balter told BostInno last week that he and the company will continue to reside here in the Boston area. Balter will report to dunnhumby’s CEO Simon Hay and join the company’s executive team.

“We are finally connecting the dots between social media and shopper marketing,” Balter remarked of the marriage of the two companies. “We are putting ROI to social media, so it is very powerful. It’s exciting to match dunnhumby’s scale in helping manufacturers know how to sell and our ability to understand social.”

BzzAgent will be using data from dunnhumby’s loyalty cards to scale its audience capacity and track individual returns to marketing campaigns based on things like cardholder data and purchase cycles.

After Communispace was acquired this February in Boston, we had the chance to conduct an in-depth interview with Balter to understand exactly how BzzAgent is displacing the myth that social media isn’t measurable. We also wrote about how the company is finally getting Gen Y to listen based on another interview with Balter in March of 2010. Both interviews underscore dunnhumby’s interest in the company:

“The customer today is as influential as the CMO was a decade ago,” stated dunnhumby CEO Simon Hay in the press release today. “Customers’ choices are influenced in many places and social media and word-of-mouth are playing a key role for brands and retailers. BzzAgent leverages a base of 800,000 influential customers in the word-of-mouth space; it is focused on measuring return on investment and the role of social media. Our focus has always been on building loyalty. With BzzAgent, we believe we can now help our clients understand advocacy and use this knowledge to earn more loyal customers for retailers and brands.”

BzzAgent was founded in 2001 to use social marketing to accelerate word of mouth to drive sales. It most recently raised $13.75 million in January 2006 in a second round of funding from General Catalyst and IDG Ventures. dunnhumby was just recently ranked in the Top 100 best companies to work for in the UK, which suggests BzzAgent and its employees will be joining an equally great culture.

Congrats to the entire BzzAgent team!