According to Apple, who noted the issue in fine print at the bottom of their website, “If you keep your iPhone in a leather case while charging with your MagSafe Charger, the case might show circular imprints from the contact.” We suppose this to be expected given that the magnets will actually pull the phone against the case, exerting more pressure compared to if you were to use it with a regular non-magnetic wireless charging mat.
We’re not sure if this was an oversight on Apple’s part during the design phase, especially since these cases are supposed to have been designed with MagSafe in mind. That being said, Apple only mentions leather cases.
We’re not sure if plastic cases or silicone cases will end up with similar problems, but there are several casemakers who have already started to design cases for use with MagSafe, so those might be worth checking out if you’re not into leather or want to avoid this issue completely.