I just shot a wedding on Monday. One guy with his P&S kept stepping in front of me. I had to move over about 5 times. After a while, I just side stepped him. My 2 assistants never got in my way. They know better. But I always wonder what guests are thinking when they block the pro? It's not just inconsiderate, but just kind of clueless. I didn't say anything. My 7D with 70-200 2.8 IS would have whacked him in the head if I was really bothered. But as a guest, I never bring anything. If you really want to shoot a few shots, please be sensible to the pro. One camera, one lens, and that would be the 17-55, you can always crop later. If you are only shooting in the back to catch the ceremony, make sure you don't have a flash and shoot with the 70-200 at f2.8 and pray the lighting is good. Just having fun is a good thing, but it's the B&G's day, so catch the stuff the pro isn't getting, and if the pro comes over and tells you to stop, respect that. I never do that, as I think everyone should enjoy the event, but sometimes, pros get very territorial.