Many of our users in our organisation use the Adobe Analytics suite on Macs and whenever they need to update Ad Hoc they are prevented from installing it due to corporate security policies, they end up having to get their security policies temporarily changed to allow the install. Our policies aren't very strict so I'm guessing a lot of Mac users have similar issues.
There is a bit of software on Macs called Gatekeeper, by default this prevents software being installed if it's from an unidentified developer. If Ad Hoc was registered with Apple then this problem will go away. Here's a link to a brief article describing the issue/resolution: