Following up on a conversation with a co-worker this morning, something struck me as obvious. One of the things Sugar OS handles really well (either as sugar-on-a-stick or on the OLPC XO laptop) is simplifying the file/resource paradigm to make it consumable by children, by basing access on chronology rather than hierarchy, reminiscent of a search engine rather than a file system. Also, on Sugar you work with activities rather than files.
What struck me recently is that on the one hand, movement towards a cloud OS reflects a shift in consumer tastes from tasks like email (where you attach files in order to share) to social networking (where you pass around links and participate in activities in order to share), so when somebody asks me, in the context of a cloud OS, "but how will you be able to locate your files?" my initial reaction is this: either chronologically, or collaboratively (or possibly spatially, but that is a separate issue).
Think about it this way: was the document or picture I am trying to find something I touched recently? That should make it easy to find. No? Is it something I shared or created with another person or group of people? That narrows the field. As I add in more relationships with people who may have come in contact with the activity in question, I have fewer and fewer activities to sift through.
I think the desktop of the future will not be a desktop at all, it will be more like a shared light-box, emphasizing transparency. In order to find something again easily, you must give it relevance, and the best way you can do this is to share it, to make it available to the people with whom you already have instantiated relevant relationships.
Far more intriguing to me, while at the same time quite far out, is the idea of a spatial desktop, where the first question you ask when you want to locate a particular item is where was I? Where was I when I took the picture? Did I participate in this activity at work, on a plane, at home, in the living room or in the dining room? On the one hand, this sort of information might not be readily available for many activities, but if it were, how quickly would that narrow the field if you could recall your location when you took that picture?
The advantage of this approach is obvious as well. If you can't locate the actual picture, you can ask who else was there? Be prepared for parallax.