Apple has a tendency to shut down interesting workarounds they didn't anticipate -- and while Zwapp's all opt-in, sysctl can just as easily be used by an ad network to get more context for targeting. At that point the feature bounces from security researcher to tech press to class-action troll to grandstanding politician, and then it goes away, leaving Zwapp in a bind.
I wish Apple would allow users to explicitly give an app permission to see their installed apps. App discovery's still a huge problem.
We still hope that creating little app stores with your friends helps to solve the fundamental issue that the App Store is simply becoming too big to find useful apps fast