I'm not sure that's true. Without the names, "being on the lookout" means that you have to look at everyone and think about whether or not they're using simila

I'm not sure that's true. Without the names, "being on the lookout" means that you have to look at everyone and think about whether or not they're using similar tactics (i.e. "they could be anyone"). With the names, the first step of "being on the lookout" is checking the known-bad list, which could make you less vigilant with everyone else (i,e. "at least I know this person isn't one of them"). That It would be an irrational mistake to make, but I suspect it would also be a common one.