Social-shopping start-up Mertado.com has been acquired by Groupon, the latest in a string of acquisitions by the Chicago-based daily-deals company. The price was not disclosed.

Mertado, which launched in April 2010, lets consumers find and buy products through social networks, including Facebook. The acquisition comes only four months after Mertado raised $2.3 million in a round from Rustic Canyon, Redpoint Ventures, Y Combinator, and Blumberg Capital. The Redwood City, California-based company, a member of the YC spring class of 2010, had a total of $3.3 million in investments.

Mertado founders Mehul Shah, Rajiv Bhat and Vijay Chittoor will join Groupon. Chittor, the CEO, previously was director of product management at Kosmix, and worked as a consultant for McKinsey.

Groupon acquired at least six companies in 2011. 

"Mertado has shown a great level of innovation in the social commerce space, for example, the launch of Mertado TV, combining lifestyle video content and product selection," a Groupon spokeswoman said. "We're looking forward to leveraging the team's expertise."

Mertado, which will shut down Feb. 28, said in a statement on its website: "Groupon has been a pioneer in social commerce in many ways, and when we started talking with them, it became extremely clear that they shared the same set of values as us."

With the announcement, Mertado included a link to Groupon Goods, the online retailer and competitor to Amazon that Groupon launched in September.

The daily deal industry is projected to bring in $4 billion in revenues by 2015, says a BIA Kelsey report. But the industry is shrinking. According to a report by Daily Deal Media, “by the latter half of 2011, the industry saturation, along with the lack of return on investment, caused investors to pull back on funding."