I have always prided myself on taking time to explain everything my clients wanted explained to them. Of course it can get quickly to a level of detail where they are giving you the "deer in the headlights" look, so that's when you regroup. For any geek that thinks this is a waste of time based on the intelligence of your client, remember that if you can't explain something to a 7-year-old, you probably don't understand it very well yourself!