That's right. I often have mixed emotions on this one. Let's say we have some type of site that profiles different items. For example, the latest thing over the past few years is tagging... and it's cool. I'm trying to make up my mind on what is better: categories, tagging, or both (in terms of setting up a site with such functionality). If I do tagging, I'm thinking about limiting it to something.
What are your thoughts? Are both needed?
One problem is if I do only tagging, I don't want to do a tag cloud... because then some items that have smaller tags would be smaller and probably not get as much attention (assuming the tag cloud shows tags font sized based on how much it's used).
And then, if I do only tags, do I make it user-defined, or do I define it myself for people to choose? For as much as I'd like to say user-defined, I'm not sure how I'd display all of the tags.
I'm kind of leaning towards tagging, limit to 5, and pre-defining the options (similar to what this site does). Being able to easily find the items if someone was clicking through the site is also noteworthy.
What do you want for the tags? How will they be used? Will you have search functionality where people can type in tags and find what matches all the tags, or any of the tags?
I am not crazy about limits on tags, as you may have some products that have many tags, as they can have many uses or be multi-cultural.
But, you could do as this site, and just allow that if people have been active enough on the site then they can add new tags, and after some amount of usage they can start to go over the 5 tag limit, as it is expected that they will understand how tags should work.
The only real difference between tags and categories is the amount of words to describe something, and that tags are user-defined.
If you have certain words allowed, then it is more like categories, in usage, IMO, and that is fine. It depends on what your expectation is, your user story on how it will be used, as that would help decide the best approach.
For example, on a project I am working on, we will have categories, but these can be flexible, so you can have descriptions like:
gloves heavy-duty leather, which would be three categories, as the user may not create new descriptions, the administrator would have to allow a new word. This way the reports will have a set limit of words that are being reported on, so I can pull up a report on all gloves or all leather gloves and know I am not missing something.