My experience from C3 was that it depended a bit on the line and the person. I didn't go for any of the most popular people (those with the separate line system). I made it my thing to get a photo of me, my stuffed wampa and the person I got the autograph from. Nobody said no, and most people got up and posed in front of their table. For some I just had to bend over the table to get a photo, but as I said no problems. On the other hand I had just 2 or 3 persons behind me at most.