It's iffy. Some are well glued on and rip the cactus' "head" off and some come off easier. I've had success removing some before (removed some flesh in the process, but 6 months later it healed just fine and you wouldn't know it was the same cactus). Others, it practically killed off the top because it removed so much. Positioning of the fake flower seems to make a difference too. Their growth point is in the center, so having it glued slap dab in the center (and glued really well) makes it harder to remove.
