Players who are level 1 or 2 rarely have their flag displayed. I don't know the cause of that, but I'm gonna make a bold assumption and say that the most common flag on this site is no flag at all.
The flag is based on the location of your ip for the last few logins. There is still some unclarity whether that is for 2 logins, 10 logins or some other number.
If a player does not have a flag, they haven't logged into their account at least twice.