Tagging, in general, leverages natural language. You tag as you would normally speak or use language in every-day life. And that’s a strength of tagging–one that makes it popular and scalable and usable and all that good stuff.
Why, then, don’t all tagging system use comma-separated tagging input mechanisms? There is nothing natural about these tags–either in entering them or using them:
- socialnetworking (del.icio.us)
- to-read (del.icio.us)
- notionalbookfestival (flickr)
- newyorkcity (flickr)
Note that I’m complaining that there is no preferred term for these concepts, rather that the form that the systems require people enter tags in have caused people to find workarounds. Namely, entering compound tags (i.e., tags with 2 or more terms) isn’t how people naturally type. That you get multiple forms of tags for “New York City” is fine with me–a Good Thing even. But where there is a workaround, there is surely a fault in the system or workflow.
Consider this: “york” consistently appears in flickr’s top tags tag cloud. Really? Are so many people traveling to the lovely city of York in the UK and posting photos to flickr? Well, no. People are going to New York City and tagging their photos in a way that they would normally type: new <space> york <space> city, instead of the system-required newyorkcity or new_york_city or new-york-city. Here’s any example of a user doing that on flickr.
So, combined with the photos from the city of York that are tagged as such, “york” as a tag on flickr gets boosted up to a top tag.
WordPress does it right: you can simply type like you would an email or blogpost or whatever, using commas to separate compound tags.
itsamysterytomewhywetoleratesuchnon-user-friendly_systemsforenteringtags_whenasimplesolutionis-certainly-just-around-the-corner
Entering tags should always be comma-separated. Punkt.
EXPERIENCING INFORMATION 
I believe you are correct in this. There was also a recently rather heated debate on the subject on SIG-IA. Can’t remember what the outcome was though:
http://www.info-arch.org/lists/sigia-l/0807/0043.html
Thanks for the tip to the SIGIA-L thread. I’ve not been following that. Good to hear that others are thinking in the same way.
Cheers.
Thanks for posting this. I found your post googling as to why flickr doesn’t use commas to separate tags. I refuse to use compound-word tags, so my friends get to joke me about all the “the” tags in my sets. : )
Completely agree. One question we’re faced with now, however, is what about tags that contain a comma. Things like Richmond, Virginia, where, again, you don’t want to confuse the content’s association with Richmond, California or any other Richmond, and you don’t want to invent a new term like rva or richmondvirginia. How do you keep the association of Richmond to Virginia?
@Ian –
One thing you could do is introduce a syntax so that something like double quotes would override the comma as a separator of tags. “Richmond, Virginia” would then appear together. But I also think just having Richmond Virginia appear without the comma is a lesser evil than having to write RichmondVirginia or Richmond_Virginia.