In my case, I need to categorize user created lists of places/
organizations. I can either have user defined categories or use tags.
My obvious concern with tags is that the use of synonyms can potentially
fracture the usefulness of the data and creation of meta-noise. For Eg.
if the users are creating a list of high-schools- they could be
potentially tagged as schools, school, educational institution etc. But
it does work well in Flickr/delicious etc.