Nice link on monster customers, eek.
As an Owner/Operator of my own service oriented business I have had a few of those. One who is infamous to my friends and family (six calls during the Superbowl) but that's another story. This is certainly not the case with my customer. We are both reasonable people and want the best solution for all parties. I wasn't expecting to hand out everything so I was caught on my heels just a little. A good lesson on being clear at the beginning I think.

It is nice to hear some of the best practices regarding this because it can be a touchy subject that I can see might get out of hand. Like tilt said, when you hand out all your layers and whatnot you are handing out secrets to how you do things that may have taken you a long time to discover. An interesting point as well that if someone makes a few tweaks to a layer and posts it on the Internet it might not be the best representation of your work. Hopefully, there would be a note that it's been modified but you know how the net can be.

I think this is a case where my user can really benefit from having the layers (so they can modify over time as events unfold). I think that simplifying the layers and passing that on is a good solution. As artist I will have my original work and the customer will have everything they need. I can flatten my mountains from 3 layers into 1, etc and it will be an easy thing for them to change when necessary.