I think there is a disconnect here.
What has made App Stores successful is that they do control the transactional part of the relationship, so they can get the kind of margins you need to make them viable. Force.com generates subscription revenue, takes a cut of app sales, and ties customers deeper in to their own platform with each app install (resulting in higher long-term lock in).
If you don’t have those advantages, you are not an “app store” as people are discussing them, you are a directory.
Oneforty is not an app store, it is a directory of Twitter apps. It is simply positioning itself as an app store. Oneforty cannot offer developers the value-add they need, nor can they offer end-users the unified and integrated experience that they love in real app stores. It is a tough spot to be in.
Building a directory of twitter apps is a much different proposition than Salesforce building force.com and I am surprised people are confusing the two so easily.