I have seen several scopes that were crinkled by overtightening. You can partially collapse a scope very easily by cranking too hard. Popular 1" hunting scopes do not have very thick aluminum walls and they will wrinkle, collapse or gouge very readily. Tactical scopes are more resistant to collapsing as their walls are somewhat thicker.
Depending on where the rings are the result can range from purely cosmetic damage to binding the power ring or effecting the adjustment mechanism.
Badger Ordnance recommends 15 inch pounds or 1.2 foot pounds for the TORX cap screws that hold the two pieces of their rings together. One very knowledgable gunsmith told me that is about the torque that can be applied by holding the allen wrench by the short portion, rather than cranking with the long portion.