The Rise and Fall of Groupon's Andrew Mason Groupon's former chief executive, Pinterest's edge in ecommerce, Wanelo's funding round and more social-media news.

This week's need-to-know social-media news.

Two years ago, it seemed as though Groupon's Andrew Mason could do no wrong. With an unorthodox resume -- he earned a degree in music from Northwestern University -- and an offbeat leadership style, he founded and led the Chicago-based daily deals site to an impressive IPO, with a $12.7 billion valuation. All in a span of three short years. But the era of Mason as Groupon's CEO ended yesterday, and an interim leadership team is taking over as the company searches for a new chief executive.

In a memo to employees, Mason was bluntly honest about his dismissal. "If you're wondering why I'm leaving," he told them, "you haven't been paying attention. From controversial metrics in our S1 to our material weakness to two quarters of missing our own expectations and a stock price that's hovering around one quarter of our listing price, the events of the last year and a half speak for themselves. As CEO, I am accountable."

Now, four years since its launch, Groupon's valuation has dropped more than 75 percent to just $3 billion. It remains to be seen whether the daily deals giant can improve its market position now that Mason's legacy is in the rearview mirror. -- The New York Times

For one big brand, Pinterest trounces Facebook in ecommerce.
Beauty products brand Sephora has announced that its Pinterest followers spend an average of 15 times more on Sephora products than its Facebook fans. Julie Bornstein, Sephora's head of digital, explains that Pinterest puts users in the mindset of "acquiring items," while Facebook remains largely a "customer interaction tool." If more ecommerce companies find this to be true, Pinterest's valuation -- currently $2.5 billion -- could climb rapidly. -- VentureBeat

Social site Wanelo gets funding.
If you thought Pinterest drove impressive online sales, get ready for Wanelo, a hot new ecommerce startup that allows you to bookmark items and buy them through direct links to online stores. The company just closed its initial funding round, raising between $5 million and $10 million, at a valuation of more than $100 million. "If Pinterest is the magazine, then Wanelo is the catalogue," one investor told TechCrunch. -- TechCrunch

Facebook buys Atlas Advertiser Suite, still isn't launching an ad network.
Facebook said it will buy Microsoft's Atlas Advertiser Suite, a media measurement platform that allows advertisers to deliver and track the results of their campaigns. But Facebook's Brian Boyland doesn't wan people to get the wrong idea. "Why we're doing this is not to launch an ad network, and why we did do this is to improve measurement," he told TechCrunch. "We heard loud and clear from advertisers that they want to understand multi-touch attribution instead of just looking at the last click." So Facebook advertisers should be hopeful that the acquisition of Atlas means they will soon be getting some much-needed insight into the return on their ad investments. -- TechCrunch

Reuters and Wall Street Journal socialize.
On Twitter this week, news service Reuters announced its intention to up its social engagement. Translation: It's going to trade in automated tweets for a human who will monitor and respond to the company's followers. In doing so, Reuters received some friendly ribbing from fellow publisher The Wall Street Journal. @Reuters tweeted, "Yes, it's true: Reuters is listening. We welcome you to share ideas on Reuters.com, Twitter, Facebook, and Google+." @WSJ replied, "Good to see you guys playing catch up over there! Just kidding, hope you are enjoying interacting more with your followers." To which the person running the @Reuters feed responded with a GIF that, well, has to be seen to be understood. -- Canada.com