(…okay, next to taking the money and running.)
The biggest sin I see committed is when publishers sell their backed products to the general public well before backers get their copies.
Seeing the tweets today about the new Kindle, and how people who ordered day one — the alpha consumer base — have not received theirs when peope who have ordered later are getting packages today.
Now, I know enough about dealing with fulfillment when I worked with Indie Press Revolution to know that fulfillment glitches happen pretty often. This is a big, noticeable one, but I’m not surprised. However, it does remind me of the problem I’ve seen with a number of pre-order and Kickstarter campaigns in the RPG world: after your money is taken, you’ll find it available at Gen Con before you’ve received your copy.
When you do that, you’re sending a clear message that your alpha customers are only valuable to you for their money, and not after that. Now, sometimes that’s not the intended message — when I spoke with Graham Walmsley briefly at Gen Con about Stealing Cthulhu being available for sale while my backer copies hadn’t been shipped yet. he seemed apologetic. I didn’t leave the conversation with a sting, but I will think twice now about backing something else he does.
See, backing & pre-ordering is about trust and, in this very small world, relationships. Show that you don’t value them, and see what happens. I had such a reaction at Gen Con 2010 from Luke Crane, when his Adventure Burner was on sale at the show and people had not yet received their pre-order copies. I commented on this and he blew me off, which told me not to pre-order anything of his again. I saw on Twitter that people did get their copies of Burning Wheel Gold before Gen Con, so it’s cool that he learned from his mistakes there.
Unless you have a fan base that will forgive you for your sins, don’t do this. It takes a lot of work to repair gamer/consumer trust & relationships.
This happens on accident with people who are new to publishing, because new folks always underestimate the time it takes to do, well, everything involved. If you find this happens, gracefully apologize and explain the situation. And, you know, learn from your mistakes. :)
 Or British. I’m not sure.
 There’s another lesson in how, if you have a rabid, cultish following or create books that are critical to conversations online, you can abuse expectations and people’ll keep coming back. Hell, I bought Burning Wheel Gold at Gen Con.
 Edit: Though, apparently Graham has publicly called me a troll for pointing out my consumer reactions to his Kickstarter fulfillment. That is an unfortunate display of character.