There's no mechanism capable of averting tag decay. If there were, it would be in Reddit Enhancement Suite and I would not be posting on hubski. The truth is, the best way to moderate public tag-based communities so far has been blacklisting, either of users or keywords. Several approaches have been attempted, including personal blacklists, moderator blacklists, and democratic blacklists (up/down voting). Repeatedly, the massive inhuman scale of internet communities has demonstrated that effective blacklisting of individuals from public communities is infeasible. Hubski's userwhitelist+tagblacklist approach inverted this, and has the potential to scale better than the tagwhitelist+userblacklist approach. Any desire to follow tags is just conservatism or nostalgia. It is the side-effect of remembering the old comfortable paradigms of reddit and the like.