This image shows the dialog box that a user received when trying to install Molleindustria’s already-censored game Phone Story. Turns out this is a lauded “anti-malware” feature called Gatekeeper in OS X Mountain Lion.
Users can change the settings, but many people experience the misleading dialog above, not telling the user the truth – that they cannot install the program because they have to enable non-certified apps/developers in system settings. But rather telling the user that the file is “damaged”.
Paolo has a longer discussion of it here, but it does seem like that Apple has made it possible for the dialog to mislead in order to dissuade users from installing software not sold through the Mac App store and/or made by a licensed developer.
[Note: It is unclear whether this dialog is intentional. Some people claim that it is not the default dialog, but some developers experience it nonetheless.]
I wrote about this scenario some time ago as “Fear of an App Planet“: that our ability to easily and transparently develop and distribute games for PCs and Macs is gradually eroding. Worrying.