Having read the about Butler, and taking into account the considerable thought and concepts already expounded, I'd like to suggest an aspect to the conversation that may prove more relevant over the next 18 months. The consumption of Drupal sites by mobile devices is actively being addressed, but there is also an increase in the number of mobile applications that are accessing the content of Drupal sites directly through services, and allowing mobile users to interact with that content within that application. An excellent example of this was just presented @ DrupalCon in Chicago.
In addressing mobile application usage of services from a Drupal site, the different use-cases of mobile devices themselves alter the paradigm of the "always-on" connection required to use the content of a site. Because people who use mobile devices invariably take them places where there is no connection, an application will need to address the issue of storing, syncing, queuing, aging, and proving the general logic to govern data traffic-directing. While this obviously can be handled within the implementation of services, I will posit that the architect of this system (Drupal site, mobile application[s], mobile use[rs]) may want to actively govern the decisions that have to do with the traffic-directing, not to mention the interaction with content.
That said, I'd encourage all of us involved to consider what level of abstraction/constraints/rules/logic that you want to be addressable within the head-space of this initiative governing services to mobile applications and their users. I don't have any definite recommendations at this time, but want to shine some light on what I see as a surging user-base by the time that D8 comes to fruition, and enjoin a conversation.
