Copying from http://www.mono-software.com/Mono/Pages/Discussion/dtopic/LgbbbC6xcEWjFaD9AJZe1Q/Social-tagging-and-tag-clouds/
since this is a suggestion (added some more text compared to the original entry in bold below):
1) Is there any social tagging facility planned? That is apart from the author of an item (say one published in a gallery, or a blog entry etc.), other users could attach their own tags that are shown to them for that item apart from those the author set and also are suggested to other users when they do add tag, or also shown for the item if enough users have added that tag (say >10 users, configurable by the admin). Author of the item should maybe have option to disable and keep hidden a social tag used by many other users (to avoid group bullying on one's content).
It's nice to see that on http://scratch.mit.edu
that does something like that in fact that one shows you all tags used by users for an item and you can endorse or reject them by pressing a tick and an X button next to each one - maybe if you are the owner of an item rejecting one could mean that it is no more suggested to other users for the item [only shown to those users who had added or endorsed that tag for your item])
2) A tag cloud widget would be also useful in this case. It would have two uses:
(a) one use of it would be when seeing an item's page (say a blog post or a page about a chosen gallery item), where it would show a cloud of social tags (so you'd see with bigger font the most used tags on that item)
(b) the other use would be when seeing a gallery or all blog posts together and you see a cloud with which tags are mostly used for the items in the collection (maybe there the widget would have an option to use only the author tags from each item or use the social tags [from all users] from each item to calculate the social tag cloud [that is the tags mostly used in the set of the items in the collection of blog posts or gallery items])