It always bugged me, so there is a certain range where you can stand with ranged hero and get blue with no damage what so ever. Mostly AD carries, like MF, Varus, Vayne can pull this of at early levels (like 1-3). Also with little or no HP at later levels.
I did this with Ahri just to demonstrate.
Is this fair? Perhaps it is just intended this way, cause ADs are weaker than other champions.