If there is another giant / ogre / whatever with reach, next to the one you are attacking you would provoke from it. But the feat is pretty clear, you do not provoke from your target. If you want to hit the ride-by attacker, when it charges you, you must ready an attack :) If you successfully tumble through a threatened square, you do not provoke. Ride-by is the same thing, it's an exception based on the feat. Here is what is on page 66 of the FAQ Will a reach weapon (or natural reach) allow you to make an attack of opportunity against a foe using the Spring Attack or Ride-By Attack feats against you? Don’t you always get an attack of opportunity against a foe that moves in to make a melee attack against you when you have greater reach than that foe? What about a 5-foot step? If you have greater reach than your foe, won’t you get an attack of opportunity against a foe that uses a 5-foot step to get close enough to attack you? Having superior reach allows a creature to threaten more squares, but it doesn’t allow that creature to make attacks of opportunity when it otherwise could not. When you use either Spring Attack or Ride-By Attack, your movement does not provoke attacks of opportunity from the foe you attack using the feat. (The benefit from Ride-By Attack also extends to the mount.) Indeed, one of the main purposes of both of these feats is to allow you to close with foes that outreach you without getting smacked with an attack of opportunity. Remember, however, that neither feat prevents attacks of opportunity from creatures that you’re not attacking. A 5-foot step provokes no attack of opportunity from anyone if that step is your only movement for the round, no matter how much reach those foes have. Again, one of the reasons the 5-foot step rule exists is <a href="http://www.wizards.com/default.asp?x=dnd/er/200302" rel="nofollow">http://www.wizards.com/default.asp?x=dnd/er/200302</a>... It seems to confirm it, the target gets no AoO.