Reuters: Mike Lazaridis and Jim Balsillie have bowed to investor pressure and resigned as co-CEOs and co-chairmen, handing the top job to an insider with four years at the struggling BlackBerry maker. Thorsten Heins, a former Siemens executive who has risen steadily through RIM’s upper management ranks since joining the Canadian company in late 2007, took over as CEO on Saturday, RIM said on Sunday.