funky2004:Moreover, vast majority of users did not use it or did not care about it.
Probably due to the bugs of the feature and growing limitations. I tagged all my requests even my oldest ones and nearly every tag got lost after some hours/days. I readded them and they got lost again. This repeated itself so often, that I made backups of my tags per thread, to be able to readd them within minutes. I'm sure, most of the others affected by this problem didn't have this endurance. I myself stopped readding lost tags for some months until few days ago due to lack of time. Then, some weeks ago tag-cloud disappeared from main site and it was not possible to filter by multiple tags anymore. The latter was a really hard cutback. Nevertheless, I was able to recognice the positive effect of tags in my requests. To say, the users were not interested, is the easy way out.
Of course the bulk of people does not invest much time in it's request. They don't search, they don't check if they provided links generate proper previews and of course they will not put tags on their requests, they prefer to b*mp instead. But others will do it if you let them. Take a look at themes. Nearly every thread up to the last page got a thumb and I bet that 95% of them were not provided by the ones who made the request. That's the reason why I always asked to enable editing of previews for all users of all requests. Let people edit the tags of every thread and I predict we'll get most threads categorized.
funky2004: Most users who used it made a big mess of it.
That was before tags got restricted to threads. Some users thought "more is always better" and tagged every single post. Of course all their posts to a thread got mainly the same tags. With the limitation of tags to threads the noise of useless or redundant tags was daramtically reduced and IMO acceptable. Of course it could have been better with some rules and more lead.
If people see some good examples in tag cloud they will follow. I tried this with tags like "80s", "90s" or a leading "by " for tags naming a photographer and in fact some people followed many of these examples in the short time these tags were up.