del.icio.us is part of what has been called the 'social software renaissance', using something called 'tagging'. Tags are usually one word -- like a keyword --
applied to something on the web. Tagging organises information on the web, on a user-lead, bottom-up basis, or so the theory goes, rather than being organised from on high. For this reason it is sometimes called a "folksonomy". That is to say a sort of categorisation done by 'the people', not the 'experts' (these are 'Taxonomies').

Take a look at the del.icio.us web site, if you have not before, to get an idea of what this means. It is in fact easier to grasp than many of the commentaries
might lead one to believe. There are many good articles on del.icio.us and folksonomy in general. For del.icio.us: http://bokardo.com/archives/the-delicious-lesson/; for folksonomy, http://en.wikipedia.org/wiki/Folksonomy.

IOU.s concentrates not on the tags but on the "user notes". With all the discussion of tagging these get left out of the picture.
The "user notes" are.... notes written by the users (about the web resource). They are more revealing than the tags in some ways. They are an opportunity
for the writers to express themselves at greater length than the tags allow.  Having read a lot of them, one of the things that is
quite striking is the amount of product endorsement. This suggests the possibility that companies are tagging their own products.
What happens if the users 'on the ground' are also the people 'up there'? What if the folksonomist is in fact a taxidermist? (sorry, taxonomist...)