I'm a newly-self-published author of a fantasy novel (16th January, and a pile of books are arriving from the POD's printer today!). I have loved Book Crossing since a friend introduced me to it last October. It ties in with my personal philosophy and has provided hours of entertainment, fresh perspectives, and friends - tomorrow is my third "in real life" BX meeting here in Sunnyvale.
I've been fascinated by the concept and have actively looked *forward* to being a Book-Crossing author since day one! I don't think BX detracts from sales; I would tend to think it enhances them. As an author, I'd be *happy* to know that people enjoyed my book and were willing to share it with others... the exposure it brings is probably going to be quite important to me, as other authors in this thread have noted.
Admittedly, I have a different perspective from one whose only source of income is royalties; I will be handling my own sales, for the greater part (online book stores come later, etc etc). But I think that anything that encourages people to read, think and get to know one another has to be a great plus.
Linda Moore (whiteraven13)
http://www.rhaeva.com <-- novel