G'day Mgm,
Pottercast/PotterCast (and podcasts in general) Forums and Blogs Bands (C-Moon - German, is it vanity or not?) Schools (examples shouldn't be needed for this one), although I have to admit discussion is pretty much growing on this. I'm sure this will eventually lead to notability guidelines.
All these could be covered by some number statistic and notability guidelines, but a quick test to easily determine its deletion worthiness is much harder. Doesn't mean we shouldn't try to find one, though.
Bands are a good example. In theory, we could say "failing WP:MUSIC makes them speediable". But there's always a chance that we might want to keep articles on some of the bands which fail WP:MUSIC ... and that's what AfD is for.
AfD isn't for *deleting*, it's for *keeping*. AfD is the compromise between geni's "admins can delete anything they like" idea and Anthony (and others') disguised "nothing verifiable should be deleted, ever" idea.