So i was thinking that for those of us who have an open tag system (i.e. where tags do not have to be defined within a predefined set): when someone enters a tag for a forums post, blog entry, etc. etc., is it possible to have a responsive list of existing tags come up based on user input, much like when you type @ followed by a user name a list of users comes up based on your input?

I think this might help avert typos and, hence, the unintended creation of more tags than is necessary.

Great idea!