There has been a little shake-up at New York-based PubSub Concepts, one of the original RSS tracker services. Long time CEO, Salim Ismail, known for his flamboyant shirts and no-nonsense manner has left the company. He has been replaced by Constantine Spathis. In an email to several of his contacts, Ismail said he was leaving for several reasons, and wrote, “When I started PubSub, it was always the intent to build it to a certain point and then leave to do my next venture. After four years (internet years, no less), that time has come.” Is something major is clearly afoot at the company? There have been acquisition rumors doing the rounds for a while now. More details to follow.