Apple has apparently started removing an increasing number of apps that allow users to search App Store contents and recommend apps to their friends. Apps that have been found to violate App Store regulation 2.25, which prohibits apps that could be confused as app stores, have been removed, and Apple seems to be broadening the scope of that rule. According to PocketGamer.biz:
As a result, it appears Apple has stretched the remit of 2.25 to cover sharing via email or social networks. The ability to search the App Store within third-party apps also now seems to be restricted.
This crackdown hasn’t been applied to alls apps with this similar functionality, nor is the removal of such apps anything particularly new. AppShopper Social was removed from the store late last year when it was still just AppShopper for similar reasons. It came back towards the end of last month, while it still seems to violate the rules. Perhaps it slipped through the app review cracks, or maybe it technically complies with the rules. Apple has yet to comment on increased enforcement of restrictions.