Actually I think it works more like 2 separate ladders. If you're searching for opponents, you can only pair up with people who are hosting which resulted in you, playing on the right side. If you're hosting, you can only play against people who are searching for opponents resulting you being on the left side. To sum this down, you will never play against people who are searching when you yourself searching as well. Same thing with people who are hosting. Skill/rank/whatever...means zippo.
-free