Yeah, I'm just thinking in terms of making the curation worthwhile for the user. We already have community tags that need to be improved. I'm just wondering if there might be some nice synergistic way to make the curation process bring immediate returns for the people doing it. I had the thought that community tags could be rolled into this functionality, but I don't think that necessarily works. Community tags aren't necessarily used as 'similar' tags, but for editorialism or greater or less specificity.
To make it worthwhile to me, all you need to do is work it into tag discovery. Say I go to the page of all things that are titled #writing. It asks me if I want to follow #writing. It might also suggest #writebetterdammit, #writingsucks and www.readwriteweb.com. If I can click "similar" next to #writebetterdammit, then you have metadata suggesting that at least one user thinks #writebetterdammit is similar to #writing but #writingsucks and www.readwriteweb.com are not. If I also have a radio button that says "follow and group" next to all, that's another piece of metadata for you. Finally, on my page let me rename my "groups" so that "#writing#writebetterdammit" becomes "Writing" (or "kleinbl00's magical writing group"). That's more metadata for you. The trick is to make that grouping pleasant and fun. I'd go as far as to say handing out badges for every (20? 40? 100?) grouped tag would be altruistic; after all, those badges don't do you any good, they're the gift that keeps on giving. Spitballing.
That's not a functionality problem, that's a UI problem. Take it from an engineer - the two are NOT the same. Wanna see how MOTU's Digital Performer won Digital Audio Workstation of the year for 2011?