Suppose a fighter with the Step Up and Following Step feats is standing next to an ogre with ten-foot reach. On its turn, the ogre takes a 5-foot step away from the fighter. The fighter can now use her Step Up or Following Step feat to move up to the ogre.
It is clear what happens if the fighter uses Step Up. She makes a 5-foot step, so she does not provoke an attack from the ogre. However, she also loses 5 feet of movement on her next turn.
What if the fighter uses Following Step to move ten feet (maybe one square sideways, and then one square towards the ogre)? Does she provoke an attack from the ogre for moving within its reach?
What if she uses Following Step to move five feet directly towards the ogre? Does this provoke an attack, or is it treated like a five-foot step?
It seems very odd to me that using this feat would cause you to suffer attacks of opportunity, but I can't think of a reason why it wouldn't.