I boarded a plane SFO-DFW and took my seat in Y, my upgrade having not cleared. At the end of the boarding process (the plane was full), I was approached and told my upgrade had cleared. I had made myself comfortable in seat 10A on the 757 and had just had a meal on my flight hours earlier, so I asked the guy who had been assigned my seat in Y if he wanted to sit up front. He of course said yes, but the FA stated that it was me, not him, who was upgraded, and that I should to F. I didn't really care enough to protest or to delay the flight any more, so I just got up and moved. But is this a policy, i.e., that you can't give your upgrade to someone else?