Bo seems to be told a couple of times that there are a whole range of different Fae types, and in The Mourning After, Saskia mentions that that there are a number of types of succubus. Given that there must be a number of each type, this makes for a pretty huge population of Fae.
So why does no-one notice all of these Fae, all of the killing, all of the deaths? I realise that Dyson works hard to keep them hidden, but it seems that with all of these Fae around, with all of the activity that they pursue, why does no-one at all see and remember anything?
Please avoid spoilers (or use the spoiler markup) from any episodes after season 1, The Mourning After.