This is a case where these service should be able to survive outside the App Store as mobile websites, but I simply don’t see what problem Apple is solving by keeping them out of the store.
It’s strange that after Apple acquired Chomp and redesigned the App Store app, it seems to be harder to use the app and harder to find new titles. Yet Apple doesn’t want third parties to help them solve the discoverability problem.
Update (2012-10-04): Federico Viticci:
I believe Apple’s main “issue” is with apps that look like an alternative App Store, containing links to App Store apps. By avoiding “similarity” and “confusion”, Apple wants to ensure users will rely on Apple’s App Store for search and discovery, not a third-party App Store lookalike. If you think about it, it makes sense for Apple to want people to use the App Store: more people means more data, more data should lead to better Genius and Search results over time. From this standpoint, I’d argue Apple wants users not to just open direct links in the App Store, but to use the App Store.