"I think that marking people clearly cheapens the game. I like the chaos of not knowing. It forces players to think and it forces teams to develop security. How many times has a lone player strolled up to your command bunker and eliminated everyone, despite multiple security check points, just because everyone assumed they were friendly? Those are great moments for everyone."
I think that chaotic element is a lot of fun too, especially when you're the one doing it. From the point of view of someone running a game though where you want to keep as many customers happy as possible, it can get irritating. Some people (myself included) go through a LOT of work to make some moves on the field pay off, and having an hour or two worth of movement getting cut short by Johnny-trigger-happy is genuinely rage inducing. On the other hand, I've had people walking towards me that didn't answer a challenge question or are shooting at teammates and when I shoot them, they reveal they were team members. It happens.