Breen did not respond to a message sent via Facebook, but he has been posting columns recently on The Huffington Post that allude to new personal aspirations, and describe him as an "entrepreneur."
IPG declined to comment, but a prepared statement indicates that Breen left of his own volition and may in fact be pursuing a new venture.
"Bant Breen has left Reprise Media to pursue outside interests," it states, adding, "We wish Bant the best of luck in his future endeavors. As we orchestrate a deeper alignment among our digital brands, as announced by Mediabrands in April, Reprise will continue to operate as a world-class search organization that powers the IPG network. We look forward to announcing a number of exciting moves in the coming weeks."
Breen's social media profiles on Facebook, LinkedIn and Twitter continue to describe him as worldwide CEO of Reprise, a post he picked up last September after serving as global digital chief for IPG's Initiative unit.
Early in his IPG career, Breen was seen as a rising star who might one day take its digital or media helm, or maybe even a bigger post, but was moved around following a number of reorganizations of its digital and media operations until his last role at Reprise, an acquisition Breen oversaw for IPG in 2006, and one of the few big takeover deals IPG has completed in recent years.
But his highest profile contribution to IPG undoubtedly is the relationship he struck with Facebook, which resulted in a stake estimated to be about 0.5% of the social network's equity. Some analysts have put the current value of Facebook at more than $100 billion, and believe it could reach as high as $200 billion following an initial public offering.
While IPG took the stake for strategic reasons, and not for a capital pay-off per se, the value of the investment is considered a happy accident inside IPG.
In his most recent posting on The Huffington Post, Breen writes about the value of staying in touch with old friends in a hyper-connected digital world. In his previous post, he discusses an inflection point he recently had when he turned 40, which resulted in a personal goal to run a marathon.
"At 40 I found that many things that were personal were getting pushed to the side for work and family commitments," he wrote, adding, "This goal setting seems to be working. My muscles tend to rebel a bit at times, but I am now five weeks into training and just passed the seven-and-a-half-mile mark on my long run. As I jog toward this marathon, I am more open to setting personal goals again. Maybe I will climb a big mountain, sail around something or think of new challenges. In the meantime I will keep running."