i'm working on social networking site and currently trying to figure out a way to create something similar to facebook's "interests" section. (ex. i type in a comma separated list of my interests and they show up in my profile as links to a search query of ppl with that interest.)
it seems that "tagging" oneself with interests can automatically provide links to the taxonomy term corresponding to the interest, and there are lot of taxonomy modules to provide addt'l functionality...but i have a few questions:
-in your opinion should i use taxonomy/tagging for this or something like the node hierarchy.module?
-can you provide any insight into how i could possibly get the following accomplished:
--a) have the link result in a view that would search through multiple content types (forum topics, organic groups and other users) in that particular taxonomy term
--b) have multiple categories of tags - like [type of organization], [areas of focus], [location], etc. - and display them separately - right now, even though there are multiple fields in the profile, all tags display right-aligned at the bottom of the page.
i would appreciate any insights, as right now i'm just fumbling around trying to figure it out. thanks!

Comments
There's a new module called
There's a new module called alink that might help you.
And old one
There's a user_tags module, sometime ago I post a patch http://drupal.org/node/245582 for 6.x branch
My set up
Sorry, I forgot to mention my set up:
I'm using Drupal 5 with Advanced Profile Kit and Bio to control profiles.
any progress
Hello! I'm looking for something similar as you. I know that this was a while back but any insight to your choice of development would be helpful.
I'm also building a social networking site to connect people of similar interests. When a user selects associates themselves with a node content I want the node content to display all of the users interests associated to that node.
I also need a feature like your's and facebook. A user can enter an interest in a text field that will automatically generate a list of interest. Like an autocomplete. I understand the technology to use for this is AJAX.
My biggest wonder is how to obtain all of the interests and categories from facebook. Do you know of any databases out there that will support this objective? Did you go with a taxonomy system or a hierarchical node system?
I am looking into the Drupal Module Interest - http://drupal.org/node/140708 . I haven't implemented yet but I believe this module can support my needs. Now it's how do I obtain a full database of vocabularies.
Thank you Drupal Community!