TAT founder Hampus Jakobsson announced via Twitter that he is leaving RIM. Jakobsson has been a part of RIM since The Astonishing Tribe (TAT) was acquired back in December of 2010. TAT has been working hard on the BlackBerry 10 UI due out early next year and has contributed much to the upcoming OS. The TAT team at RIM is pretty much in place by now, so his departure shouldn't really affect what comes in BlackBerry 10.
I'm handing over this to others in RIM now. but if you want to follow me as an ex-TAT-founder I'm at: @hajak
It's unclear as to why Jakobsson decided to leave RIM, but on his new Twitter account he noted "cause I'm a startup-guy and even if I really liked the company and the people, I felt it was time to start another one ...".