Since before the Mac App Store opened, there were people already opposing the model. The Mac App Store emulates Apple's iOS App Store in the sense that apps need to be submitted for approval. Just like the iOS App Store, apps are subject to be rejected if they don't follow certain guidelines.
An alternative to the iOS App Store is Cydia, but that requires users to jailbreak their iOS devices. The HackStore doesn't, despite the suggestive name. The HackStore will take all those apps that wouldn't get into the Mac App Store, but won't accept pirated apps or will allow piracy.
It works just like the Mac App Store; the HackStore is an app that you install on your Mac. In it you will find apps, but also tweaks for Mac OS X, that were not accepted or are not available in the Mac App Store.
It even has Growl integration for notifications. Users will upgrade their apps within the HackStore, just like the Mac App Store allows.
It is great that there are more alternatives out there, especially for the Mac. But curation from piracy and malware needs to be always present.