yeah you would need to get those rugged cases (Lifeproof, Otterbox, etc) or any case that has a strong frame (those Element Cases, Devilcases, strong metal/aluminium bumper style cases etc). cause even those using Apple's original leather case also can end up bending their phone (someone posted an article last time, the guy used the red leather case and his phone was bent) so you would need something really sturdy to minimize or totally avoid the possibility of it bending. but it also depends on your luck lah, like most users in this thread did not report any bending yet with the case that they're using so i'm guessing their phones are still okay. if want to use those slim cases have to be extra careful.