Hampus Jakobsson, who founded currently RIM-owned UI developer group The Astonishing Tribe (TAT), just announced that he has left RIM to pursue other projects. Jakobsson made the announcement in a tweet from TAT's account, saying he was "handing it over to others in RIM."
When asked why he had left, Jakobsson said he was a "startup guy" and felt it was time to found another one, even if he "really liked the company and the people" at RIM. Swedish company TAT was acquired by RIM in 2010 to polish the interface of BlackBerry phones and the ill-fated PlayBook tablet; its UI work formed the basis for BlackBerry 10's Cascades interface. TAT says that Jacobsson's departure won't stop the now-established team from continuing its work, and BlackBerry 10 is (hopefully) in its final stages of development, so the change shouldn't affect it too much. Still, it's hard to see this as anything but another RIM departure.