I went to the wikipedia article linked in the 23things list and just for kicks looked at the history. Just that day there were three edits, one undoing an earlier one from that same day. I compared the undone one with the current one. What was undone? A lengthy wandering diatribe against assorted topics. I really don't like nor trust Wikipedia, but that's not part of the Thing 13 discussion.
Anyway, this whole social bookmarking thing raises the issue of user created tags versus a controlled vocabulary (such as LCSH). Being a cataloger by training I see the need and benefit of a controlled vocabulary. Playing with one of the Flickr mashup games over the weekend my s.o. and I were frustrated in trying to guess the common tag. What seemed to be an appropriate tag to us ended up being a synonym to the tag used. As terminology changes (is the USB thing in my purse a jump drive, a thumb drive, a flash drive?) tags will no longer match what people are searching for.
On to Del.icio.us (how does one easily remember where to put the periods?) A couple of years ago I attended a workshop on blogs, wikis, RSS, etc. I was introduced to Furl.net and began using it for saving and tagging some of my bookmarks. I like it because furl.net is a lot easier to remember and type than del.icio.us. I don't make use of all it's features because I haven't found a need for them.
Many websites seem to now have links to "Save to del.icio.us" That makes it very convenient if you do not want to install the delicious toolbar and don't want to take the extra step of going to the delicious website. I've not seen a Furl link. It was also very easy to upload all my Internet Explorer bookmarks into Del.icio.us and then update the tags. I was able to figure out what old bookmarks may no longer work based on the number (or absence) of people sharing the bookmark. That was useful.