Ebook pricing for sci-fi and fantasy

The Pet Dragon is now free! Yay!
I'm experimenting with the prices of my ebooks. The question is, what is a fair price for a full novel in ebook format? It's not an easy question to answer and, in fact, there’s a fierce debate about what ebooks should cost. It's well known, for example, that raising prices will lower sales, and so this got me to thinking that the opposite must most likely be true.

I've decided to take this to its logical conclusion and make one of my books free. Here's the link to get a free copy from Smashwords. The reason I'm doing this isn't because I've gone crazy or no longer need money for food to eat, there's some strategy behind the decision.
Free books can be downloaded hundreds of times more often than other books, at any price. Nothing attracts reader interest like a book being given away for free, and this will, theoretically, create a huge pool of readers who are hungry for more of my writing, and who will be willing to pay to read it.
The Huffington Post, arbiter of all things Internet, says in this article that  if pricing is done right, a book's sales will increase through viral word-of-mouth. That's the plan for this book. It will introduce me to a lot more readers, and this will increase sales of the other books I've written. I think the key to building a brand as an author and therefore build a fan base, is more important to long term success than maximizing the amount of money that can be made on any one single book. Anyway, it's the first time I've ever reduced the price of a book down to zero, and it will be interesting to see what the results of the experiment turn out to be.