It probably has implications for all books written by fans. Less well-known authors would be glad of the attention. If someone wrote a companion or lexicon for other books presumably they could be sued on similar grounds, which would be a shame for some books because they benefit from guides. There has to be a fair-use compromise. I presume the Potter Lexicon website comes under fair-use, but the book doesn't.
There are unauthorized Discworld guides and Terry Pratchett hasn't sued the authors. So maybe each author takes it their own way.
It's trolling - duh. Audience figures for the VMAs were up 15% on 2007, 70% on 2006, in the 12-34 demographic. All of the people getting annoyed about it are unwittingly promoting the person they hate. There's double the traffic on the MTV site than last year - due to butthurt fans. Twice the traffic is a good thing for MTV. A lot have people have been trolled. For profit. Lol.
There are unauthorized Discworld guides and Terry Pratchett hasn't sued the authors. So maybe each author takes it their own way.