I had to sort of laugh, because this happened in my blogging circle about 6 months ago. A lot of people believed this fake blog and bought into it. People started sending the author, whom they thought was a young college girl, letters, pouring their hearts out about similar experiences they had with the blogger, etc. And she used these letters to write more posts, and in fact, threatened to shut down the blog because there were some people who didn't believe she was real, which of course fueled even more letters of support.
Then, it came out who it was, and it was actually a well known blogger in this particular circle.
There were A LOT of angry people. The people who write this fictional character felt embarrassed and humiliated, and I can see why. The real blogger posted about it on her blog, and finally stopped allowing comments because people were getting so nasty. She and I have since talked about it and I told her that I think that once she started getting heartfelt letters, she should have come clean.
She too was offered a book deal, but apparently didn't follow through and it fell through.
I think it depends on how it's handled. I feel like my friend's gaffe was not allowing comments on the fictional blog, but allowing emails and accepting them, incorporating people's real feelings and emotions for what sort of amounted for her own gain.