I think that is a very important point. I've been arguing for quite a while that tags and social bookmarking can be revolutionary for LOR because now we can make a connection between the user, the resource and its metadata.
Before, it was only the resource and metadata, and a scary looking form for searching the resources (this is time before Google's simple search box, right?). Now, if implemented correctly, social bookmarking and tagging not only helps individuals with their resources management (e.g. Favourites), but also helps other folks to find resources through other users and their digital traces such as tags, number of bookmarks, etc.
To understand Activity Theory it is important to get the bases: everything, well, everything within human activity, is based on the three dominant aspects which are production, distribution and exchange (or communication).
The model suggest the possibility of analyzing a multitude of relations within the triangular structure of activity. However, the essential task is always to grasp the systemic whole, not just separate connections. (no page number in my print, just below Figure 2.6).This is also the base for the analysis in Margaryan & Littlejohn (2008) for the learning resource repositories as instrument, with rules, division of labour, outcomes, etc.
Moreover, Engström emphasises that there is no activity without the component of production.
The specificity of human activity is that it yields more than what goes into the immediate reproduction of the subjects of productions. One part of this "more" is the surplus product that leads to sharing and sociality, discussed by Leakey & Lewin and Ruben above...(found on the next page)
I was thinking of folksonomies and how the production of tags is first of all good for me. People often times tag and bookmark to "keep found things found", it's part of personal knowledge management activity. Similarly like above, when referred to, for example, production of food that leads to sharing and sociality, in tags, the fact that they are made available to all, leads to sharing and sociality.
I thought that was pretty neat.