I'm not a call maker, just a call buyer- so my take maybe slightly different.
I don't necessarily think it's wrong, especially if the callmaker brings the customer off to the side, and doesn't sell calls right in front of a booth. No rules are being broken, so as long as the guy walking around is discreate, there shouldn't be any problems. On the other hand, a guy selling calls shouldn't be made to feel as if he's in a drug deal, sneaking back to rooms, and going in to restrooms to sell a pot call!
Lets all be honest. If someone wants to buy a call from a guy at a booth he will. Chances are, the guy in the aisles is being sought out buy the buyer- and that's who he wants to buy from. Having a booth isn't going to change that...