I have previously written asking (and sort-of answered) What is Content Management?.
My definition of content: Labeled, linkable data.
I go on in that post to talk about the attributes of Content Management, contrasting it with related ideas like Knowledge Management.
I have just realized that tagging systems like del.icio.us let you make content out of stuff you don't own, or can't change. Adding a tag is labeling something, in a way that makes it linkable, discoverable. I even use it on my own site to add categories like ContentManagement.
So if del.icio.us is a content management system, then by my way of thinking a web page sitting on someone's server is 'just' data until it is tagged, at which point it becomes a del.icio.us content item. This is the same kind of distinction that people make between data and information for humans; you need information to construct knowledge, just as the content management system needs content to manage content.
Why am I telling you this?
I find the simple working defintion of content really useful in evaluating solutions to various problems in and around content management. Is this going to give me labelled data and I can use to make links?
Why do we want to make links?
Links help humans use to construct knowledge, collections of unlinked data don't help.
Of course labeled data is good for more than links - if you label some parts of your documents as headings, for example, then you can get a table of contents for free. So next time someone is demonstrating a 'Content Management' system to you ask if it can give you a table of contents for each item. I reckon that tells you whether or not it's really managing content.