Android lost a major ally at Samsung Mobile this week, with the departure of Omar Khan. The CTO is leaving the hardware manufacturer for the industry analyst side of things, joining Citigroup's mobile solutions team. Khan has led the charge on a number of Android-based devices, including, recently, the S II and various other products in the Galaxy line -- he also made a memorable appearance on The Engadget Show, back in August of last year. Samsung's Nick Dicarlo and Gavin Kim will be stepping in to grab some of Khan's PR responsibilities at the company.