At the moment there's a badge for the first tag wiki edit, but could we do with silver / gold badges along the same lines? After picking a bunch of random tags it seems few of them have decent wiki summaries apart from the really popular ones (Java for instance) and it seems that at the moment there's little incentive for people to create any more.
Perhaps a silver badge for say 50 tag wiki edits and a gold for 100? Numbers are arbitrary, it's just the concept I wanted to get across.
EDIT: As pointed out the existing badges go some way towards this, but it's poorly documented so I'd imagine people just don't know. Perhaps the badge descriptions should be updated to reflect this?