Add Into dialog slow if lots of collections for groups

With a user that has a lot of collections and groups, select to "Add" a resource in to an existing personal or group collection.

The first dialog appears quickly, but when you move to open the group collections section (And to a lesser degree the "My Collections" section) the AJAX spins for a minute or more depending on the number of items. It seems the API is loading way more data then it needs to in order display the requested tree.

This process must be made faster as the most powerful users see it when they do the most common activity.

There are probably at least two closed items related to this...