As most of you well know, Toykopop releases the majority of manga around here (others include Dark Horse and Viz), and aside from printing the manga in the original sequence (left to right) they also have ratings on the back of the comics. I think it's great that they do that.
However, since Toykopop is intent on staying on the cutting edge, they are importing some of the first official English yaoi manga. Two series that you'll see in your local manga pick-up are "Gravitation" and "Fake." Although these have material that many people find objectional, they are keeping the rating system the same as if it were a guy/girl theme instead of guy/guy. So, you could pick up a manga that has a good rating, but get a rude surprise later on.