I get it. Great costumes are great. Pictures of great costumes are also great. There are many, many great costumes to take great pictures of at Dragon*Con. And it's really tempting to, in spite of signs that say "No Photography," think, "I'll just snap a quick picture. I mean, it's Princess Leia next to Leeloo Dallas, and Bender is with them! How can I pass that up?"
The trouble is, that temporary stop in forward motion attracts the attention of everyone else who is toting a camera. Before long, the whole hallway is blocked with a series of one quick pictures.
So, I'm not going to name any names. There's no Wall of Shame here. But apart from anywhere with a posted "No Photography" sign, these are, by far, the worst places to take a picture at Dragon*Con. (And most of them apply to any other convention, too.)
5. In any busy area where money is being exchanged for goods and services. That includes the dealer's rooms and the food court during the lunch rush. All those people trying to exchange said money for said goods take priority here. And there are lots of them.
4. Across any hallway or breezeway. I said this in a comment on a blog once, and I got the reply, "To be fair, sometimes there's nowhere else to do it." A more accurate assessment would be, "Sometimes there's nowhere both the photographer and subject are willing to travel to do it." That nice clean background of the hallway wall is pretty, but taking pictures across the hall creates a logjam while everyone else waits.
3. Anywhere you have just stopped abruptly and without warning to take a picture. Signal before you turn.
2. At a street corner where people are trying to move from the sidewalk to the crosswalk. Especially since some of these people are civilians.
1. Anywhere near or in any of the Dragon*Con host hotels or along the parade route immediately after the parade. Take as many pics as you want during the parade, but let the mad rush of traffic clear once it's over before you get the camera out again.